EXHIBIT 5.1

August 4, 2015

National Instruments Corporation

11500 North MoPac Expressway

Austin, Texas 78759

Re:           Registration Statement on Form S-8

Ladies and Gentlemen:

We have examined the Registration Statement on Form S-8 to be filed by you with the Securities and Exchange Commission on or about the date hereof (the “Registration Statement”) in connection with the registration under the Securities Act of 1933, as amended, of 5,518,416 shares of your Common Stock reserved for issuance under your 2015 Equity Incentive Plan. The 2015 Equity Incentive Plan is referred to herein as the “Plan” and the shares of Common Stock reserved for issuance under the Plan are referred to as the “Shares.” As your legal counsel, we have examined the proceedings taken and proposed to be taken in connection with the issuance, sale and payment of consideration for the Shares to be issued under the Plan.

It is our opinion that, when issued and sold in compliance with the applicable prospectus delivery requirements and in the manner referred to in the Plan and pursuant to the agreements that accompany the Plan, and upon completion of the actions being taken or proposed to be taken to permit such transactions to be carried out in accordance with the securities laws of the various states where required, the Shares, when issued and sold in the manner described under the Plan and the agreements that accompany the Plan, will be legally and validly issued, fully paid and non-assessable.

We consent to the use of this opinion as an exhibit to said Registration Statement and further consent to the use of our name wherever appearing in said Registration Statement, and any amendments thereto.

Very truly yours,

/s/ Wilson Sonsini Goodrich & Rosati

WILSON SONSINI GOODRICH & ROSATI

Professional Corporation