Exhibit 32.1

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Annual Report of INTL FCStone Inc. (the Company) on Form 10-K for the period ended September 30, 2017 as filed with the Securities and Exchange Commission on the date hereof (the Report), I, Sean M. O’Connor, Chief Executive Officer of the Company, certify, pursuant to 18 U.S.C. § 1350, as adopted pursuant to § 906 of the Sarbanes-Oxley Act of 2002, that to the best of my knowledge:

(1) The Report fully complies with the requirements of section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

(2) The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

Dated: December 14, 2017

/s/ SEAN M. O’CONNOR

Sean M. O’Connor

Chief Executive Officer

A signed original of this written statement required by Section 906 or other document authenticating, acknowledging or otherwise adopting the signature that appears in typed form within the electronic version of this written statement required by Section 906, has been provided to INTL FCStone Inc. and will be retained by INTL FCStone Inc. and furnished to the Securities and Exchange Commission or its staff upon request.