James Cameron's blockbuster adventure Avatar was found to be the most pirated movie in Hollywood history, according to a study released by TorrentFreak.

The film has been downloaded some 21 million times since its 2009 release. Ironically, Cameron had famously touted 3D filmmaking as the industry's best defense against piracy.

Despite the enormous number of illegal downloads, Avatar was still able to net nearly $2.8 billion in worldwide theatrical gross.

Here's a list of the top 10 most pirated films ever:                                                                      

Avatar (21 million downloads)

The Dark Knight (19 million)

Transformers (19 million)

Inception (18 million)

The Hangover (17 million)

Star Trek (16 million)

Kick-Ass (15 million)

The Departed (14 million)

The Incredible Hulk (14 million)

Pirates of the Carribean: At World's End (14 million)

Source: movies.yahoo.com