Omar Bakri Muhammad (Arabic: عمر بکری محمد‎; born Omar Bakri Fostock in 1958 in Syria) is an Islamist militant leader who was instrumental in developing Hizb ut-Tahrir into a major organization in the United Kingdom before leaving the group and heading another Islamist organisation, Al-Muhajiroun, until its disbandment in 2004.

For several years Bakri was one of the more well known and high profile Islamic radicals based in London, and was frequently quoted and interviewed in the UK media. He vowed in December 2004 for example that Muslims would give the West "a 9/11, day after day after day," if Western governments did not change their policies. He has been described both as "closely linked to al-Qaeda" — he released prepared statements from Osama bin Laden after the 1998 United States embassy bombings — but also as the "Tottenham Ayatollah," who was "long been regarded as little more than a loudmouth."

In 2005, following the 7 July 2005 London bombings the Times reported that "a dozen members" of his group Al-Muhajiroun "have taken part in suicide bombings or have become close to Al-Qaeda and its support network." Shortly after, he left the UK, where he had sheltered for 20 years, for Lebanon. While there he was informed by the Home Office that he would not be allowed back into the UK.