A flamen was a priest of the Roman religion.

The etymology of the word flamen is obscure. Some Indo-Europeanists have attempted to link it to the Sanskrit word brahman; this etymology is controversial.

There were fifteen flamines in the Roman republic. The most important three were the flamines maiores, who served three Roman gods. These flamines were required to be patricians:

• Flamen Dialis, who worshipped Jupiter
• Flamen Martialis, who worshipped Mars
• Flamen Quirinalis, who worshipped Quirinus

A fourth flamen maior was added after 44 BC dedicated to Julius Caesar.

The remaining flamines could be plebeians. Some of the deities they worshipped were rather obscure, which suggests the antiquity of the institution and the pre-republican origin of these priesthoods:

• Flamen Carmentalis, who worshipped Carmentis
• Flamen Cerialis, who worshipped Ceres
• Flamen Falacer, who worshipped Falacer
• Flamen Floralis, who worshipped Flora
• Flamen Furrialis, who worshipped Furrina
• Flamen Palatualis, who worshipped Palatua
• Flamen Pomonalis, who worshipped Pomona
• Flamen Portunalis, who worshipped Portunus
• Flamen Volcanalis, who worshipped Vulcan
• Flamen Volturnalis, who worshipped Volturnus

The robe of office of a flamen was a special priestly hat called an apex, and a wollen coat called a læna. When the Imperial cult got under way, further flamines were appointed to worship the divine Roman emperors.