Around one million people are now downloading the Facebook application for the iPhone every month, helping make it Apple's most popular free app.
Nearly seven million people have now signed up, which represents almost 25% of Facebook's 30 million mobile users around the world. Blackberry meanwhile has five million.
This comes just a few days after the social networking site announced a major new milestone - with its 200 millionth member.
CEO Mark Zuckerberg said: "Creating channels between people who want to work together towards change has always been one of the ways that social movements push the world forward and make it better."
Since last August it's been adding, on average, 500,000 new users every month.