The Fast and the Furious sequel racked up 9.2 million downloads to take first place ahead of The Hangover Part II, which was pirated 8.8 million times.
File-sharing blog Torrent Freak places Marvel Studios' Thor in third place, ahead of Source Code and I Am Number Four, in fourth and fifth, respectively.
Sucker Punch came in sixth, followed by 127 Hours in seventh. Rango, The King's Speech and Harry Potter and the Deathly Hallows: Part 2 rounded off the top ten.
James Cameron's Avatar was named as the most pirated film of 2010 this time last year, with more than 16 million illegal downloads.
Torrent Freak reported that this year's piracy figures show a decline compared to 2010, a trend it attributes to the increasing popularity of file-sharing and streaming sites.
The top ten list of 2011's most pirated films is as follows:
1. Fast Five - 9.2m downloads
2. The Hangover Part II - 8.8m downloads
3. Thor - 8.3m downloads
4. Source Code - 7.9m downloads
5. I Am Number Four - 7.6m downloads
6. Sucker Punch - 7.2m downloads
7. 127 Hours - 6.9m downloads
8. Rango - 6.4m downloads
9. The King's Speech - 6.2m downloads
10. Harry Potter and the Deathly Hallows: Part 2 - 6m downloads
Watch a trailer for Fast & Furious 5 below: