Bêl (; from Akkadian: bēlu), signifying "lord" or "master", is a title rather than a genuine name, applied to various gods in the Mesopotamian religion of Akkad, Assyria and Babylonia. The feminine form is Bêlit 'Lady, Mistress' in Akkadian. Bel is represented in Greek as Belos and in Latin as Belus. Belit appears in Greek form as Beltis (Βελτις). Linguistically, Bel is an East Semitic form cognate with the Northwest Semitic Baal with the same meaning.

Early translators of Akkadian believed that the ideogram for the god called in Sumerian Enlil was to be read as Bel in Akkadian. Current scholarship holds this as incorrect, but one finds Bel used in referring to Enlil in older translations and discussions.Bel became especially used for the Babylonian god Marduk and when found in Assyrian and neo-Babylonian personal names or mentioned in inscriptions in a Mesopotamian context, it can usually be taken as referring to Marduk and no other god. Similarly, Bêlit mostly refers to Bel Marduk's spouse Sarpanit. However, Marduk's mother, the Sumerian goddess called Ninhursag, Damkina, Ninmah and other names in Sumerian, was often known as Belit-ili ("Lady of the Gods") in Akkadian.

Other gods called "Lord" could be and sometimes were identified totally or in part with Bel Marduk. The god Malak-bel of Palmyra is an example, though in the later period from which most of our information comes he seems to have become very much a sun god.

Similarly, Zeus Belus mentioned by Sanchuniathon as born to Cronus/El in Peraea is unlikely to be Marduk.

In Mandaean cosmology, the name for Jupiter is Bil (ࡁࡉࡋ), which is derived from the name Bel.