The full game, which is the number one app of all time, has been made free as part of Apple's "App of the Week" promotion, in a move that represents the first time iOS users have been able to get their hands on the full version of the app since it launched in 2009 on iPhone and 2010 on iPad.
Despite being free to download, there are still in-app purchases for extra items and power-ups.
In addition to the price drop, Rovio has also added 15 new levels for the 'Bad Piggies' episode of the game.
Rovio's decision to offer the original Angry Birds for free has shot the game up into the top spot in the Top Free Apps chart for both iPad and iPhone.
Free sampler versions of Rovio's Angry Birds apps have been offered since January 2011, but never before have the full versions been free on iOS. On Android, the app has long been free, but it contains in-app ads.