Muslim Bulgarians (also Bulgarian Mohammedans, bul:Българи-мохамедани; local: Pomak, Ahrian, Poganets, Marvak, Poturnak) are descendants of Christian Bulgarians who were forcibly converted to Islam by the Turks, during the 16th and the 18th century. The word pomak is derived from Bulgarian dialectal pomaka (torture) and pomacen (tortured). Those who accepted Islam voluntarily are called Poturnak, meaning "One who turned into a Turk".

Muslim Bulgarians live mostly in the Rhodopes – the Smolyan region, the southern part of the Pazardzhik and Kurdzhali districts and the eastern part of the Blagoevgrad district in Southern Bulgaria and the Xanthi and Rhodope provinces in Northeastern Greece. They also live in a group of villages in the Lovech region in Northern Bulgaria.

Muslim Bulgarians speak a variety of archaic Bulgarian dialects. Under the influence of mass media and school education, the dialects have been almost completely unified with standard Bulgarian among Muslim Bulgarians living in Bulgaria. As Greece has tended to regard its Muslim minority as only Turkish-speaking and has allowed only education in Turkish, the Muslim Bulgarian community in Greece has become largely bilingual and the mother tongue of some of its members now is Turkish. The spoken language of those members of the community who have preserved the dialect as their mother tongue has been influenced to a large extent by Turkish and Greek and shows many aberrations from formal Bulgarian.

Muslim Bulgarians do not represent a homogenous community in Bulgaria. Those living in the eastern and central parts of the Rhodopes (the districts of Smolyan region and Kurdzhali) tend to be non-practising Muslims and usually have Christian names. A large number of them, especially those living in the municipalities of Zlatograd, Nedelino, Krumovgrad, and Kirkovo, converted to Christianity in the 1990s. The ones living in Pirin and on the western fringes of the Rhodopes (in the districts of Pazardzhik and Blagoevgrad) are, however, strongly religious and have preserved the Muslim name system, customs and clothing. Whereas the majority of the community has identified itself as Bulgarian in the population censuses in 1992 and 2001, a certain minority in the Western Rhodopes has opted for Turkish ethnicity although its mother tongue is also Bulgarian. The name ‘Pomak’ is strongly pejorative in Bulgarian and is resented by most members of the community, especially by non-practising Muslims. The name adopted and used instead is Bulgarian Mohammedans (Muslim Bulgarians).

The Muslim Bulgarian community in Greece has been largely Turkified. Since the 1990s Greece has made tentative attempts to promote a separate "Pomak" identity, partly because of the advanced Turkification of the non-Turkish members of its Muslim minority (Muslim Bulgarians and Roma) and partly for fear of the growing percentage of Muslims in Thrace in the past couple of decennia. A Greek-Pomak dictionary has been issued and Muslim Bulgarians have frequently been described by Greek authorities as "an amalgamation of Bulgarians, Greeks and Turks" or even as "Muslim Slavophone Greeks".

There is also a substantial Muslim Bulgarian community in Turkey, estimated at some 120,000 people. These are not recognized by the Turkish government as an ethnic minority and have been largely Turkified. Some of them have Turkish or distinctive "Pomak" self-consciousness.