A mosque is a place of worship for followers of Islam. The word entered English from a French word which probably derived from Italian moschea, a variant of Italian moscheta, from either Armenian mzkiṭ or Greek μασγίδιον, from Arabic masjid, meaning "place of worship" or "prostration in prayer", from the Arabic sajada, meaning "to bow down in prayer" or "worship", probably ultimately of Aramaic origin.

There are strict and detailed requirements in Sunni fiqh for a place of worship to be considered a masjid, with places that do not meet these requirements regarded as musallas. There are stringent restrictions on the uses of the area formally demarcated as the masjid (which is often a small portion of the larger complex), and, in the Sharia, after an area is formally designated as a masjid, it remains so until the Last Day.

The mosque serves as a place where Muslims can come together for salah (prayer) (Arabic: صلاة‎, ṣalāt) as well as a center for information, education, and dispute settlement. The imam leads the prayer.