SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D/A

Under the Securities Exchange Act of 1934

(Amendment No. 48)

LSB INDUSTRIES, INC.

(Name of Issuer)

COMMON STOCK, PAR VALUE $.10

(Title of Class of Securities)

5021600-10-4

(CUSIP Number)

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

December 4, 2015

(Date of Event Which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition which is the subject of his Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f), or 240.13d-1(g) Rule 13d-1(b)(3) or (4), check the following box.  ¨

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. §240.13d-7 for other parties to whom copies are to be sent.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Exchange Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

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Introduction

This statement constitutes Amendment No. 48 to the Schedule 13D dated October 7, 1985, as amended previously (the “Schedule 13D”), relating to the common stock, par value $.10 a share (“Common Stock”) of LSB Industries, Inc. (the “Company”). All terms not otherwise defined herein shall have the meanings ascribed in the Schedule 13D.

This Amendment 48 is being filed jointly by Jack E. Golsen (“J. Golsen”), Barry H. Golsen (“B. Golsen”), Steven J. Golsen (“S. Golsen”), Linda F. Rappaport (“L. Rappaport”). Golsen Family, L.L.C., an Oklahoma limited liability company (“GFLLC”), SBL, L.L.C., an Oklahoma limited liability company (“SBL”), and Golsen Petroleum Corporation, an Oklahoma corporation (“GPC”)(each, a “Reporting Person” or a “Golsen Holder,” and, collectively, the “Reporting Persons” or the “Golsen Holders”), who report as a “group” (the “Golsen Group”) within the meaning of Rule 13d-5(b)(1) under the Exchange Act, pursuant to a Joint Filing Statement dated September 20, 2007, filed as Exhibit 99.1 to Amendment No. 34 of the Schedule 13D, and a Joint Filing Statement dated December 29, 2008 and filed as Exhibit 99.2 to Amendment No. 38 of the Schedule 13D.

B Golsen, S. Golsen, and L. Rappaport are the children of J. Golsen (collectively, the “Golsen Family”). All of the membership interests in GFLLC are owned by the Golsen Family or trusts controlled by a member of the Golsen Group. J. Golsen is the sole manager of GFLLC. All of the outstanding units of SBL are owned by GFLLC, B. Golsen, S. Golsen and L. Rappaport. J. Golsen and B. Golsen are the sole managers of SBL and the sole members of the Board of Directors and the officers of GPC.

This Amendment 48 is being filed to disclose (i) the execution of a Board Representation and Standstill Agreement, dated December 4, 2015 (“Board Representation Agreement”), by and among the Company, LSB Funding LLC (“LSB Funding”), Security Benefit Corporation, Todd Boehly, and each of the Golsen Holders; (ii) a Letter Agreement dated December 4, 2015, by and among the Company, LSB Funding and each of the members of the Golsen Group, all as more particularly described in Item 6 of this Amendment No. 48; and (iii) the termination by SBL of the 10b5-1 Sales Plan dated May 20, 2015, between SBL and Morgan Stanley-Smith Barney, LLC, previously disclosed in Amendment No. 47, which provided for the sale of up to 150,000 shares of the Company’s common stock pursuant to the terms of Rule 10b5-1 of the Exchange Act.

Item 1 of this Schedule 13D is unchanged.

Item 2 of this Schedule 13D is unchanged, except that B. Golsen resigned as President and Chief Executive Officer of the Company effective September 1, 2015. B. Golsen, who engages in investment activities for his personal account, remains a director of the Company.

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CUSIP NO. 5021600-10-4

Item 3 of this Schedule 13D is not applicable.

(i) the number of shares the member has sole power to vote or direct the voting and sole power to dispose or to direct the disposition; (ii) the number of shares the member has shared power to vote or direct the voting and shared power to dispose or to direct the disposition; (iii) the number of shares owned beneficially by the member; and (iv) the percentage of outstanding Common Stock owned beneficially by the member.

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The amount shown does not include 533 shares owned directly by Gay Golsen, B. Golsen’s wife, over which B. Golsen disclaims beneficial ownership.

The amount shown does not include 51,433 shares that L. Rappaport’s spouse owns, over which L. Rappaport disclaims beneficial ownership.

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CUSIP NO. 5021600-10-4

The filing of the Schedule 13D by the Reporting Persons, as amended by this Amendment No. 48, is not an admission that any Reporting Person, for purposes of Section 13(d) of the Act, is the beneficial owner of any shares of Common Stock included in this Schedule 13D in which such Reporting Person does not have any ownership and economic interest.

Board Representation and Standstill Agreement. On December 4, 2015, each of the Golsen Holders, together with the Company, LSB Funding, Security Benefit Corporation and Todd Boehly, entered into the Board Representation Agreement, in connection with the purchase by LSB Funding of 210,000 shares of Series E Cumulative Redeemable Class C Preferred Stock (the “Series E Preferred Stock”), (ii) one share of Series F Preferred Stock and (iii) Warrants to purchase 4,103,746 shares of Common Stock (collectively, the “Purchased Securities”), pursuant to a Securities Purchase Agreement dated December 4, 2015 by and between the Company, LSB Funding and Security Benefit Corporation.

Under the Board Representation Agreement, the Golsen Holders, collectively, have the right to designate two directors (“Golsen Holders Designated Directors”), and the Board of the Company shall nominate, and shall recommend the election of, and the vote by the stockholders for, the Golsen Holders Designated Directors. However, if the Golsen Holders, collectively, continue to beneficially own at least 2.5% (but not 5% or more) of the then outstanding Common Stock, the Golsen Holders will only be entitled to designate up to one director. These designation rights will terminate immediately on the first date on which the Golsen Holders, collectively, no longer beneficially own at least 2.5% of the then outstanding Common Stock. During the period from and including December 4, 2015 through and including the annual meeting of stockholders to be held in 2016 (including any adjournments and postponements thereof), the Golsen Holders have agreed that, provided the Company is in compliance with the terms of the Board Representation Agreement, at any meeting of the stockholders or in any other circumstances upon which a vote, consent or other approval of all or some of the stockholders is sought solely with respect to the election of directions, they will vote (or

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CUSIP NO. 5021600-10-4

cause to be voted) or execute (or cause to be executed) consents with respect to, as applicable, all of the Company securities owned by them as of the applicable record date in favor of the election of the persons named in the Company’s proxy statement as the Board’s nominees for election as directors, and against any other nominees.

Pursuant to the Board Representation Agreement, the initial Golsen Holders Designated Directors are J. Golsen, who is currently serving as a Director until the annual meeting of the Stockholders to be held in 2016 and is serving as the Executive Chairman of the Board pursuant to the terms of his employment agreement with the Company, and B. Golsen, who is currently serving as a Director until the annual meeting of the Stockholders to be held in 2018.

The foregoing description of the Board Representation Agreement does not purport to be complete and is qualified in its entirety by reference to the full text of the Board Representation Agreement, a copy of which is filed as Exhibit 99.9 hereto and incorporated by reference herein.

Letter Agreement. On December 4, 2015, the Golsen Holders and LSB Funding entered into a certain Letter Agreement. Under the Letter Agreement, subject to certain exceptions, the Golsen Holders have agreed to not transfer any of the shares of Common Stock that the Golsen Holders beneficially owned as of November 6, 2015, which includes shares of Common Stock that may be issued to certain of the Golsen Holders upon conversion of the Series B and Series Preferred Stock currently owned by such holders (the “Golsen Shares”), unless (a) LSB Funding beneficially owns fewer than 21,000 shares of Series E Preferred Stock; (b) LSB Funding delivers written notice to J. Golsen terminating the Letter Agreement; or (c) no Golsen Holder is serving on the Company’s board of directors.

Notwithstanding this restriction, the Golsen Holders may transfer up to 25% of the Golsen Shares without restriction (the “Permitted Transfer Amount”) and, under certain conditions, may transfer up to the entire amount of the Golsen Shares to a Permitted Transferee, as defined in the Letter Agreement. Each Permitted Transferee must agree to be bound by the terms of the Letter Agreement. Transfers to a Permitted Transferee are not included in the Permitted Transfer Amount, but will be retroactively included in the Permitted Transfer Amount if a transferee of Golsen Shares ceases to be a Permitted Transferee. Additionally, the Permitted Transfer Amount will be proportionately increased if LSB Funding transfers certain shares of Common Stock issuable upon exercise of a warrant. Additionally, the restrictions contained in the Letter Agreement do not prohibit any of the Golsen Holders from pledging Golsen Shares owned by such holder to a financial institution providing financing to such holder.

The Letter Agreement acknowledges that shares of Company stock held by the spouse of L. Rappaport are not subject to the Letter Agreement. Shares acquired by the Golsen Holders after November 6, 2015, other than by conversion of the Series B or Series D Preferred Stock owned by the Golsen Holders on or before November 6, 2015, will not be subject to the terms, limitations, or restrictions of the Letter Agreement.

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CUSIP NO. 5021600-10-4

The foregoing description of the Letter Agreement is not complete and is qualified in its entirety by reference to the full text of the Letter Agreement, a copy of which is filed as Exhibit 99.10 hereto and incorporated by reference herein.

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SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

DATED: December 21, 2015.

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Exhibit 99.10

LETTER AGREEMENT

This Letter Agreement is entered into this 4^th day of December, 2015 (this “Agreement”) by and among Jack E. Golsen, an individual (“J. Golsen”), Steven J. Golsen, an individual (“S. Golsen”), Barry H. Golsen, an individual (“B. Golsen”), Linda Golsen Rappaport, an individual (“L. Rappaport”), Golsen Family LLC, an Oklahoma limited liability company (“Family LLC”), SBL LLC, an Oklahoma limited liability company (“SBL LLC”), and Golsen Petroleum Corp., an Oklahoma corporation (“GPC”, and together with J. Golsen, S. Golsen, B. Golsen, L. Rappaport, Family LLC, SBL LLC and GPC, each a “Golsen Holder” and, collectively, the “Golsen Holders”), and LSB Funding LLC, a Delaware limited liability company (“LSB Funding”).

WHEREAS, LSB Industries, Inc., a Delaware corporation (the “Company”), J. Golsen, S. Golsen, B. Golsen and LSB Funding are each a party to that certain Commitment Letter, dated as of November 6, 2015 (as amended, restated, supplemented or otherwise modified, the “Commitment Letter”), which sets forth certain terms of financing to be provided by LSB Funding to the Company (the “Investment”);

WHEREAS, as of 12:01 a.m., Eastern Standard Time, November 6, 2015 (the “Reference Time”), each Golsen Holder beneficially owned the number of shares of common stock, par value $0.10 per share of the Company (including shares of capital stock convertible into common stock, the “Common Stock”) set forth opposite its name on Exhibit A attached hereto (collectively, the “Golsen Shares”);

WHEREAS, as stockholders of the Company, each of the Golsen Holders shall receive direct and indirect benefits from the consummation of the transactions contemplated under the Commitment Letter;

WHEREAS, concurrent with the execution and delivery of this Agreement, LSB Funding and the Company have executed and delivered that certain Securities Purchase Agreement dated as of the date hereof (as amended from time to time, the “Purchase Agreement”) pursuant to which, inter alia, LSB Funding shall acquire 210,000 shares of the Company’s Series E Cumulative Redeemable Class C Preferred Stock, no par value per share (the “Series E Preferred Stock Shares”).

WHEREAS, as a condition precedent to the completion of the transactions contemplated under the Purchase Agreement, the Golsen Holders have agreed to execute and deliver this Agreement;

WHEREAS, capitalized terms used but not defined herein shall have the meanings ascribed to them in the Purchase Agreement; and

NOW, THEREFORE, in consideration of the mutual covenants and agreements hereinafter set forth, the parties hereto each hereby agree as follows:

1. Transfer Restrictions. Each of the Golsen Holders hereby covenants and agrees that, from the date hereof until the earlier of (a) the date LSB Funding or any Affiliate thereof, collectively, beneficially owns less than 21,000 Series E Preferred Stock Shares (as adjusted to

account for any stock split, stock dividend, reverse split or similar corporate action), (b) delivery of written notice by LSB Funding to J. Golsen terminating this Agreement, or (c) such date that none of the Golsen Holders (or any nominee thereof) is serving as a member of the Board of Directors of the Company, such Golsen Holder shall not, and shall cause any Person that it directly or indirectly owns or controls not to, sell, exchange, encumber, dispose, hypothecate, pledge (other than a pledge to a financial institution providing financing to a Golsen Holder), assign, mortgage or otherwise transfer or grant rights or interests, whether voluntarily or involuntarily, by operation of law or otherwise (“Transfer”), with or without consideration, any part or all of the Golsen Shares beneficially owned by such Golden Holder to any other Person. Notwithstanding the foregoing, the Golsen Holders, collectively, may (a) Transfer up to 25% of the aggregate Golsen Shares (the “Permitted Transfer Amount”) without any restrictions or limitations contained in this Agreement or (b) Transfer the Golsen Shares to a Permitted Transferee (as defined below). It is understood and agreed that the shares of Common Stock beneficially owned by Claude Rappaport, husband of L. Rappaport, are not considered Golsen Shares and shall not be subject to the terms, limitations or restrictions of this Agreement. Any Golsen Shares transferred to a Permitted Transferee shall be excluded from (and not reduce) the Permitted Transfer Amount; provided, that if at any time a Permitted Transferee hereunder ceases to qualify as a Permitted Transferee, the Golsen Shares subject to such Transfer shall be counted towards (and reduce) the Permitted Transfer Amount; provided, further, in the event that LSB Funding transfers (other than to an Affiliate thereof) all or any portion of the shares of Common Stock issuable upon exercise of the Warrant (as defined in the Purchase Agreement), the Permitted Transfer Amount will be proportionately increased by an amount equal to (x) the percentage of such shares transferred times (y) 75%. For example purposes only, in the event that LSB Funding transfers 10% of its shares of Common Stock issuable upon exercise of the Warrant, the Permitted Transfer Amount will increase by 7.5% to 32.5% (ie—10% times 75% =7.5%). For the purposes of this Agreement, shares of Common Stock acquired by any of the Golsen Holders after the Reference Time, other than shares of Common Stock acquired by a Golsen Holder as a result of conversion of the Company’s Series B 12% Cumulative, Convertible Preferred Stock or Series D 6% Cumulative, Convertible Class C Preferred Stock owned by such Golsen Holder as of the Reference Time, shall not be considered Golsen Shares and shall not be subject to the terms, limitations or restrictions contained in this Agreement.

2. Permitted Transferees. As used herein, the term “Permitted Transferee” means any Person that is the transferee in a Permitted Transfer. “Permitted Transfer” means a Transfer by any Golsen Holder (a) with the prior written consent of LSB Funding, (b) to any spouse or lineal descendant of J. Golsen, S. Golsen or B. Golsen for purposes of estate planning purposes, (c) to any trust which is solely for the benefit of a Golsen Holder or any of the Persons referenced in clause (b) above or (d) to any Affiliate of any Golsen Holder which is controlled by such Golsen Holder. Each Golsen Holder shall advise in writing to LSB Funding within two (2) business days prior to such Transfer of such Transfer and each Permitted Transferee, subject to the following sentence, shall deliver written acknowledgment agreeing to be bound by the terms, conditions and limitations hereof. Notwithstanding anything herein to the contrary, if any Transfer by a Golsen Holder after the date hereof of Golsen Shares is to a Permitted Transferee and such Transfer is designated by the Golsen Holders (in writing to LSB Funding) as part of (and reduces) the Permitted Transfer Amount, then the terms, limitations or restrictions contained in this Agreement shall not apply as to the shares of Golsen Shares that are the subject of such Transfer and so designated by the Golsen Holders.

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3. Representations and Warranties. Each Golsen Holder hereby represents and warrants to LSB Funding as follows:

a. The execution, delivery and performance of this Agreement by such Golsen Holder does not and will not, conflict with or constitute a breach of, or default under, the (i) the provisions of any contract, agreement, partnership agreement, trust document or other organizational agreement applicable thereto or (ii) any law, rule, regulation or statute applicable thereto; and

b. All action (whether corporate or otherwise) necessary for the authorization, execution, delivery and performance by such Golsen Holder hereunder has been taken and this Agreement constitutes a valid and legally binding obligation of such Golsen Holder enforceable against such Golsen Holder in accordance with its terms.

4. Miscellaneous.

a. This Agreement shall not be assignable by any Golsen Holder or the Company without the prior written consent of LSB Funding (and any purported assignment without such consent shall be null and void), is intended to be solely for the benefit of the parties hereto and is not intended to confer any benefits upon, or create any rights in favor of, any person other than the parties hereto; provided, LSB Funding may assign its rights hereunder to any Affiliate or other Person to which LSB Funding Transfers any of the Series E Preferred Stock Shares. This Agreement may not be amended or waived except by an instrument in writing signed by each party hereto. This Agreement may be executed in any number of counterparts, each of which shall be an original, and all of which, when taken together, shall constitute one agreement. Delivery of an executed signature page of this Agreement by facsimile, .pdf or other electronic transmission shall be effective as delivery of a manually executed counterpart hereof. This Agreement and the other Definitive Documentation executed in connection with the Investment set forth the entire understanding of the parties with respect hereto and thereto and supersede any other prior understandings, agreements and arrangements by and among the parties hereto.

b. This Agreement shall be governed by, and construed in accordance with, the laws of the State of Delaware. Each party hereby consents to the non-exclusive jurisdiction and venue of the federal courts located in Wilmington, Delaware. EACH PARTY HERETO IRREVOCABLY WAIVES, TO THE FULLEST EXTENT PERMITTED BY APPLICABLE LAW, (A) ANY RIGHT IT MAY HAVE TO A TRIAL BY JURY IN ANY LEGAL PROCEEDING BROUGHT BY OR ON BEHALF OF ANY PARTY ARISING OUT OF OR RELATING TO THIS AGREEMENT, THE OTHER DEFINITIVE DOCUMENTATION OR THE TRANSACTIONS CONTEMPLATED HEREBY OR THEREBY (WHETHER BASED ON CONTRACT, TORT OR ANY OTHER THEORY) AND (B) ANY OBJECTION THAT IT MAY NOW OR HEREAFTER HAVE TO THE LAYING OF VENUE OF ANY SUCH LEGAL PROCEEDING IN THE STATE OR FEDERAL COURTS LOCATED IN THE CITY OF WILMINGTON, DELAWARE.

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c. Each party hereto acknowledges and agrees that the rights of each party to consummate the transactions contemplated hereby are unique and recognize and affirm that in the event of a breach of this Agreement by any party, money damages may be inadequate and the non-breaching party may have no adequate remedy at law. Accordingly, the parties agree that such non-breaching party shall have the right, in addition to any other rights and remedies existing in their favor at law or in equity, to enforce their rights and the other party’s obligations hereunder not only by an action or actions for damages but also by an action or actions for specific performance, injunctive and/or other equitable relief (without posting of bond or other security).

d. All Golsen Holders agree that they are independent, will act independently and will not act in concert or as a group either as shareholders or directors of the Company. The fact that any individual Golsen Holder votes in the same manner as any other Golsen Holder is not prohibited so long as any such voting decision is made individually, not subject to any agreement between the Golsen Holders and, in no event, shall any such vote be deemed to represent a group action.

[Signature pages follow.]

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IN WITNESS WHEREOF, this Letter Agreement is executed as of the date first set forth above.

IN WITNESS WHEREOF, this Letter Agreement is executed as of the date first set forth above.

[Signature Page to Letter Agreement]

EXHIBIT A

GOLSEN SHARES

A-1

A-2