QuickLinks -- Click here to rapidly navigate through this document

FORM 6-K

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

Report of Foreign Private Issuer Pursuant to Rule 13a-16 or 15d-16 of the Securities Exchange Act of 1934

For ~~Pursuant~~the tomonth ~~Rule 13a-16 or 15d-16~~ of February 2005

~~the~~Commission ~~Securities~~File ~~Exchange~~Number: ~~Act of 1934~~000-30716

For the month of January 2005

AUTONOMY CORPORATION PLC

~~Commission~~Cambridge ~~File~~Business ~~Number~~Park Cowley Road Cambridge CB4 0WZ United Kingdom Tel: 44(0)1223 448 000~~-30716~~ (Address of Principal Executive Offices)

Cambridge Business Park Cowley Road Cambridge CB4 0WZ United Kingdom Tel: 44 (0)1223 448 000 (Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F ý Form 40-F o

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1):

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7):

Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.

Yes o No ý

If "Yes" is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b): 82- .

On ~~each of 1~~February ~~December 2004,~~ 2 ~~December 2004~~, ~~3 December 2004~~2005, ~~8 December 2004,~~Autonomy ~~10 December 2004, 13 December 2004,~~Corporation ~~14 December 2004,~~plc ~~15 December 2004, 16 December 2004, 17 December 2004 and 20 December 2004~~ (the "Company") issued a press release ~~through~~announcing the ~~London Stock Exchange~~Company's ~~Registered~~results ~~News~~for ~~Service in accordance with~~ the ~~Listing~~three ~~Rules~~and oftwelve ~~the~~months ~~United~~ended ~~Kingdom Listing Authority~~December 31, ~~announcing details of purchases by~~ ~~the Company of its own shares for cancellation~~2004. ~~Copies~~A copy of the ~~releases~~press ~~are~~release is attached hereto as Exhibit 99.1 and ~~are~~ incorporated herein by reference.

~~On 31 December 2004~~Exhibits the Company issued a release announcing that the Company was to voluntarily terminate its American Depositary Receipt program. A copy of the release is attached hereto as Exhibit 99.2 and is incorporated herein by reference.

99.1: Press Release issued on February 2, 2005, announcing results for the three and twelve months ended December 31, 2004.

Exhibits
99.1		Releases issued on each of 1 December 2004, 2 December 2004, 3 December 2004, 8 December 2004, 10 December 2004, 13 December 2004, 14 December 2004, 15 December 2004, 16 December 2004, 17 December 2004 and 20 December 2004 announcing details of purchases by the Company of its own shares for cancellation.
99.2		Release issued on 31 December 2004 that the Company was to voluntarily terminate its American Depositary Receipt program.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

	AUTONOMY CORPORATION PLC
Date: 5 January 2005	By:	/s/ ANDREW M. KANTER Andrew M. Kanter Chief Operating Officer
	By:	/s/ Andrew M. Kanter
		Name: Andrew M. Kanter Title: Chief Operating Officer
Date: February 11, 2005

~~AUTONOMY CORPORATION PLC INDEX TO EXHIBITS~~ 3

Exhibit Number		Description
99.1		Releases issued on each of 1 December 2004, 2 December 2004, 3 December 2004, 8 December 2004, 10 December 2004, 13 December 2004, 14 December 2004, 15 December 2004, 16 December 2004, 17 December 2004 and 20 December 2004 announcing details of purchases by the Company of its own shares for cancellation.
99.2		Release issued on 31 December 2004 that the Company was to voluntarily terminate its American Depositary Receipt program.

AUTONOMY CORPORATION PLC

INDEX TO EXHIBITS

Exhibit Number		Description
99.1		Press Release issued on February 2, 2005, announcing results for the three and twelve months ended December 31, 2004.

QuickLinks

SIGNATURES
AUTONOMY CORPORATION PLC

Filing Compare · AUTONOMY CORP PLC