The geography of Malaysia includes both the physical and the human geography of Malaysia, a Southeast Asian country made up of two major landmasses separated by water—Peninsular Malaysia to the west and East Malaysia to the east—and numerous smaller islands that surround those landmasses. Peninsular Malaysia is on the southernmost part of the Malay Peninsula, south of Thailand, north of Singapore and east of the Indonesian island of Sumatra; East Malaysia comprises most of the northern part of Borneo, and shares land borders with Brunei to the north and Indonesian Borneo to the south.

Peninsular Malaysia, historically known as Malaya, also known as West Malaysia or the "Malaysian Peninsula", is the western part of Malaysia that comprises the southern part of the Malay Peninsula on Mainland Southeast Asia and the nearby islands. Its area totals approximately 132,490 km2 (51,150 sq mi), which is nearly 40% of the total area of the country; the other 60% is in East Malaysia on the island of Borneo.