南海（拉丁语：Mare Australe）是一位于月球东南半球的月海，其东半部在月球背对地球的一侧。南海盆地形成于前酒海纪时期，在晚雨海纪其地层被平滑、黒色的火山玄武岩覆盖。"南海"一名首先由德国天文学家"约翰·海因里希·冯·马德勒"(Johann Heinrich von Mädler)提出，并被列入首批4531个国际天文学联合会正式认定的月球表面对象范围内。

与大多数月海不同，南海表面很不平整，布满了众多陨石坑，如"詹纳陨石坑"(Jenner)、"兰姆陨石坑"(Lamb)和"古姆环形山"(Gum)等，与很多其它陨石坑一样，这些坑内都充斥着玄武岩熔岩。

Mare Australe (the "Southern Sea") is a lunar mare located in the southeastern hemisphere of the Moon. It is 603 kilometers in diameter, overlapping the near and far sides of the Moon. Smooth, dark volcanic basalt lines the bottom of the mare. The Australe basin was formed in the Pre-Nectarian epoch, while the mare material inside formed in the Upper Imbrian epoch.