巽他古陆（英语：Sundaland）是一个生物地理学上的概念，指的是末次冰期由于海平面下降而在东南亚地区露出水面并连成一体的陆地。

巽他古陆的相当一部分地区，今日都已位于海面以下。仍然是陆地的部分，包括马来半岛、婆罗洲、爪哇岛、苏门答腊岛等。巽他古地的东界为华莱士线（Wallace Line），即东洋界与澳新界动物群的分界线。

阿非利加洲
（非洲）

南极洲

亚洲

澳大利亚洲

欧罗巴洲
（欧洲）

北亚美利加洲
（北美洲）

南亚美利加洲
（南美洲）

欧亚非大陆

亚美利加洲（美洲）

欧亚大陆

大洋洲

地质学上的超大陆

地质史上的大陆

淹没的大陆
凯尔盖朗海台 · 巽他古陆 · 西兰大陆

Sundaland (also called the Sundaic region) is a biogeographical region of Southeastern Asia which encompasses the Sunda shelf, the part of the Asian continental shelf that was exposed during the last glacial period of the Pleistocene, from approximately 110,000 to 12,000 years ago. It included the Malay Peninsula on the Asian mainland, as well as the large islands of Borneo, Java, and Sumatra and their surrounding islands. The eastern boundary of Sundaland is the Wallace Line, identified by Alfred Russel Wallace as the eastern boundary of the range of Asia's land mammal fauna, and thus the boundary of the Indomalaya and Australasia ecozones. The islands east of the Wallace line are known as Wallacea, and are considered part of Australasia.