13D Filing: Abdiel Qualified Master Fund LP and Appian Corp (APPN)

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

SCHEDULE 13D

(Rule 13d-101)

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No.     )*

Appian
Corporation

(Name of Issuer)

Class A Common Stock, $0.001 par value per share

(Title of Class of Securities)

03782L101

(CUSIP Number)

Abdiel Capital

410 Park Avenue, Suite 930

New York, NY 10022

Attn:
Colin T. Moran

Tel: (646) 496-9202

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

May 31, 2017

(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 this Schedule 13D, and is filing this schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following box.  ☐

Note. Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See Rule 13d-7 for
other parties to whom copies are to be sent.

*	The remainder of this cover page shall be filled out for a reporting persons 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).