Mare Vaporum /væˈpɔːrəm/ (Latin vapōrum, the "sea of vapors") is a lunar mare located between the southwest rim of Mare Serenitatis and the southeast rim of Mare Imbrium.

It was named by Giovanni Battista Riccioli in 1651.

It is 242 kilometers (150 mi) in diameter and 55,000 km2 (21,000 sq mi) in area, and is bordered to the northeast by the mountain range Montes Apenninus.

In the south of the mare is Rima Hyginus, a rille intersected by the crater Hyginus.

The lunar material surrounding the mare is from the Lower Imbrian epoch, and the mare material is from the Eratosthenian epoch.