UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C.  20549

SCHEDULE 13G

(Rule 13d-102)

Information Statement Pursuant to Rules 13d-1 and 13d-2

Under the Securities Exchange Act of 1934

(Amendment No.   1 )*

Riot Blockchain, Inc.

(Name of Issuer)

Common stock, no par value

(Title of Class of Securities)

767292105

(CUSIP Number)

December 31, 2019

Date of Event Which Requires Filing of the Statement

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

¨ Rule 13d-1(b)

x Rule 13d-1(c)

¨ Rule 13d-1(d)

*The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

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 (“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).

CUSIP No. 767292105 13G/A Page 2 of 14 Pages

1.	NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON Citadel Securities LLC
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a)       ¨ (b)       ¨
3.	SEC USE ONLY
4.	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5.	SOLE VOTING POWER 0
	6.	SHARED VOTING POWER 418,621 shares
	7.	SOLE DISPOSITIVE POWER 0
	8.	SHARED DISPOSITIVE POWER See Row 6 above.

9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON See Row 6 above.
10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES	¨
11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 1.7%1
12.	TYPE OF REPORTING PERSON BD, OO

¹ The percentages reported in this Schedule 13G/A are based upon 24,731,215 shares of common stock outstanding as of November 8, 2019 (according to the issuer’s Form 10-Q as filed with the Securities and Exchange Commission on November 12, 2019).

CUSIP No. 767292105 13G/A Page 3 of 14 Pages

1.	NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON CALC IV LP
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a)       ¨ (b)       ¨
3.	SEC USE ONLY
4.	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5.	SOLE VOTING POWER 0
	6.	SHARED VOTING POWER 418,740 shares
	7.	SOLE DISPOSITIVE POWER 0
	8.	SHARED DISPOSITIVE POWER See Row 6 above.

9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON See Row 6 above.
10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES	¨
11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 1.7%
12.	TYPE OF REPORTING PERSON PN; HC

CUSIP No. 767292105 13G/A Page 4 of 14 Pages

1.	NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON Citadel Securities GP LLC
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a)       ¨ (b)       ¨
3.	SEC USE ONLY
4.	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5.	SOLE VOTING POWER 0
	6.	SHARED VOTING POWER 418,740 shares
	7.	SOLE DISPOSITIVE POWER 0
	8.	SHARED DISPOSITIVE POWER See Row 6 above.

9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON See Row 6 above.
10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES	¨
11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 1.7%
12.	TYPE OF REPORTING PERSON OO; HC

CUSIP No. 767292105 13G/A Page 5 of 14 Pages

1.	NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON Citadel Advisors LLC
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a)       ¨ (b)       ¨
3.	SEC USE ONLY
4.	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5.	SOLE VOTING POWER 0
	6.	SHARED VOTING POWER 0
	7.	SOLE DISPOSITIVE POWER 0
	8.	SHARED DISPOSITIVE POWER See Row 6 above

9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON See Row 6 above
10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES	¨
11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 0%
12.	TYPE OF REPORTING PERSON IA; OO; HC

CUSIP No. 767292105 13G/A Page 6 of 14 Pages

1.	NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON Citadel Advisors Holdings LP
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a)       ¨ (b)       ¨
3.	SEC USE ONLY
4.	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5.	SOLE VOTING POWER 0
	6.	SHARED VOTING POWER 0
	7.	SOLE DISPOSITIVE POWER 0
	8.	SHARED DISPOSITIVE POWER See Row 6 above

9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON See Row 6 above
10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES	¨
11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 0%
12.	TYPE OF REPORTING PERSON PN; HC

CUSIP No. 767292105 13G/A Page 7 of 14 Pages

1.	NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON Citadel GP LLC
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a)       ¨ (b)       ¨
3.	SEC USE ONLY
4.	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5.	SOLE VOTING POWER 0
	6.	SHARED VOTING POWER 0
	7.	SOLE DISPOSITIVE POWER 0
	8.	SHARED DISPOSITIVE POWER See Row 6 above.

9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON See Row 6 above.
10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES	¨
11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 0%
12.	TYPE OF REPORTING PERSON OO; HC

CUSIP No. 767292105 13G/A Page 8 of 14 Pages

1.	NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON Kenneth Griffin
2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a)       ¨ (b)       ¨
3.	SEC USE ONLY
4.	CITIZENSHIP OR PLACE OF ORGANIZATION U.S. Citizen

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5.	SOLE VOTING POWER 0
	6.	SHARED VOTING POWER 418,740 shares
	7.	SOLE DISPOSITIVE POWER 0
	8.	SHARED DISPOSITIVE POWER See Row 6 above

9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON See Row 6 above
10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES	¨
11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 1.7%
12.	TYPE OF REPORTING PERSON IN; HC

CUSIP No. 767292105 13G/A Page 9 of 14 Pages

Item 1(a) Name of Issuer

Riot Blockchain, Inc.

Item 1(b) Address of Issuer’s Principal Executive Offices

202 6th Street, Suite 401 Castle Rock, Colorado 80104.

Item 2(a) Name of Person Filing
This Schedule 13G/A is being jointly filed by Citadel Securities LLC (“Citadel Securities”), CALC IV LP (“CALC4”), Citadel Securities GP LLC (“CSGP”), Citadel Advisors LLC (“Citadel Advisors”), Citadel Advisors Holdings LP (“CAH”), Citadel GP LLC (“CGP”) and Mr. Kenneth Griffin (collectively with Citadel Securities, CALC4, CSGP, Citadel Advisors, CAH and CGP, the “Reporting Persons”) with respect to shares of common stock of the above-named issuer owned by Citadel Securities and CRBU Holdings LLC, a Delaware limited liability company (“CRBH”).

CALC4 is the non-member manager of Citadel Securities and CRBH. CSGP is the general partner of CALC4. CAH is the sole member of Citadel Advisors. CGP is the general partner of CAH. Mr. Griffin is the President and Chief Executive Officer of CGP, and owns a controlling interest in CSGP and CGP.

The filing of this statement shall not be construed as an admission that any of the Reporting Persons is the beneficial owner of any securities covered by the statement other than the securities actually owned by such person (if any).

Item 2(b) Address of Principal Business Office
The address of the principal business office of each of the Reporting Persons is 131 S. Dearborn Street, 32nd Floor, Chicago, Illinois 60603.

Item 2(c) Citizenship
Each of Citadel Securities, CSGP, Citadel Advisors and CGP is organized as a limited liability company under the laws of the State of Delaware. Each of CALC4 and CAH is organized as a limited partnership under the laws of the State of Delaware. Mr. Griffin is a U.S. citizen.

Item 2(d) Title of Class of Securities

Common stock, no par value

Item 2(e) CUSIP Number

767292105

CUSIP No. 767292105 13G/A Page 10 of 14 Pages

 Item 3 If this statement is filed pursuant to Rules 13d-1(b), or 13d-2(b) or (c), check whether the person filing is a:

(a)	¨	Broker or dealer registered under Section 15 of the Exchange Act;
(b)	¨	Bank as defined in Section 3(a)(6) of the Exchange Act;
(c)	¨	Insurance company as defined in Section 3(a)(19) of the Exchange Act;
(d)	¨	Investment company registered under Section 8 of the Investment Company Act;
(e)	¨	An investment adviser in accordance with Rule 13d-1(b)(1)(ii)(E);
(f)	¨	An employee benefit plan or endowment fund in accordance with Rule 13d-1(b)(1)(ii)(F);
(g)	¨	A parent holding company or control person in accordance with Rule 13d-1(b)(1)(ii)(G);
(h)	¨	A savings association as defined in Section 3(b) of the Federal Deposit Insurance Act;
(i)	¨	A church plan that is excluded from the definition of an investment company under Section 3(c)(14) of the Investment Company Act;
(j)	¨	A non-U.S. institution in accordance with Rule 13d-1(b)(1)(ii)(J);
(k)	¨	Group, in accordance with Rule 13d-1(b)(1)(ii)(K).
If filing as a non-U.S. institution in accordance with Rule 13d-1(b)(1)(ii)(J), please specify the type of institution: ____________.

CUSIP No. 767292105 13G/A Page 11 of 14 Pages

Item 4 Ownership

A. Citadel Securities LLC

(a) Citadel Securities LLC may be deemed to beneficially own 418,621 shares of common stock.

(b) The number of shares that Citadel Securities LLC may be deemed to beneficially own constitutes approximately 1.7% of the common stock outstanding.

(c) Number of shares as to which such person has:

(i) sole power to vote or to direct the vote: 0

(ii) shared power to vote or to direct the vote: 418,621

(iii) sole power to dispose or to direct the disposition of: 0

(iv) shared power to dispose or to direct the disposition of: 418,621

B. CALC IV LP and Citadel Securities GP LLC

(a) Each of CALC IV LP and Citadel Securities GP LLC may be deemed to beneficially own 418,740 shares of common stock.

(b) The number of shares that each of CALC IV LP and Citadel Securities GP LLC may be deemed to beneficially own constitutes approximately 1.7% of the common stock outstanding.

(c) Number of shares as to which such person has:

(i) sole power to vote or to direct the vote: 0

(ii) shared power to vote or to direct the vote: 418,740

(iii) sole power to dispose or to direct the disposition of: 0

(iv) shared power to dispose or to direct the disposition of: 418,740

C. Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC

(a) Each of Citadel Advisors, Citadel Advisors Holdings LP and Citadel GP LLC may be deemed to beneficially own 0 shares of common stock.

(b) The number of shares that each of Citadel Advisors, Citadel Advisors Holdings LP and Citadel GP LLC may be deemed to beneficially own constitutes 0% of the common stock outstanding.

CUSIP No. 767292105 13G/A Page 12 of 14 Pages

(c) Number of shares as to which such person has:

(i) sole power to vote or to direct the vote: 0

(ii) shared power to vote or to direct the vote: 0

(iii) sole power to dispose or to direct the disposition of: 0

(iv) shared power to dispose or to direct the disposition of: 0

D. Kenneth Griffin

(a) Mr. Griffin may be deemed to beneficially own 418,740 shares of common stock.

(b) The number of shares that Mr. Griffin may be deemed to beneficially own constitutes approximately 1.7% of the common stock outstanding.

(c) Number of shares as to which such person has:

(i) sole power to vote or to direct the vote: 0

(ii) shared power to vote or to direct the vote: 418,740

(iii) sole power to dispose or to direct the disposition of: 0

(iv) shared power to dispose or to direct the disposition of: 418,740

CUSIP No. 767292105 13G/A Page 13 of 14 Pages

Item 5 Ownership of Five Percent or Less of a Class
If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than 5 percent of the class of securities, check the following x.

Item 6 Ownership of More than Five Percent on Behalf of Another Person

Not Applicable

Item 7 Identification and Classification of the Subsidiary which Acquired the Security Being Reported on by the Parent Holding Company

See Item 2 above

Item 8 Identification and Classification of Members of the Group

Not Applicable

Item 9 Notice of Dissolution of Group

Not Applicable

Item 10 Certification
By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

CUSIP No. 767292105 13G/A Page 14 of 14 Pages

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

Dated this 14^th day of February, 2020.

CITADEL SECURITIES LLC		CITADEL ADVISORS LLC
By:	/s/ Guy Miller	By:	/s/ David Glockner
	Guy Miller, Authorized Signatory		David Glockner, Authorized Signatory
CALC IV LP		CITADEL ADVISORS HOLDINGS LP
By:	/s/ Guy Miller	By:	/s/ David Glockner
	Guy Miller, Authorized Signatory		David Glockner, Authorized Signatory
CITADEL SECURITIES GP LLC		CITADEL GP LLC
By:	/s/ Guy Miller	By:	/s/ David Glockner
	Guy Miller, Authorized Signatory		David Glockner, Authorized Signatory
		KENNETH GRIFFIN
		By:	/s/ David Glockner
			David Glockner, attorney-in-fact*

^* David Glockner is signing on behalf of Kenneth Griffin as attorney-in-fact pursuant to a power of attorney previously filed with the Securities and Exchange Commission, and hereby incorporated by reference herein. The power of attorney was filed as an attachment to a filing by Citadel Advisors LLC on Schedule 13G for Roku, Inc. on January 17, 2018.