Tom Cruise: An Unauthorized Biography

Tom Cruise: An Unauthorized Biography is a biography of actor Tom Cruise, written by Andrew Morton. The book was published in the United States in hardcover format on January 15, 2008 by St. Martin's Press, with a first printing of 400,000 copies, and an audio format on five CDs by Macmillan Audio.

Cruise's lawyers and the Church of Scientology have released several statements which question the truthfulness of assertions made by Morton in the book. In an official 15-page statement released to the press, the Church called the book "a bigoted, defamatory assault replete with lies". The book was not published in the UK or New Zealand due to strict libel laws in those countries. Although initially not published in Australia, it was later published there and became popular.

The book hit number one on Amazon.com's list of top sellers three days after it was published, and was number one on The New York Times Best Sellers list one week after publication. It was the number one bestseller in Australia for publisher AbeBooks in 2008. The book received mixed and critical reviews in The New York Times. The San Jose Mercury opined that it should be taken "with the proper grain of salt."