Thoại Sơn is a rural district (huyện) of An Giang province in the Mekong Delta region of Vietnam.

The district capital lies at Núi Sập.

[2] The "Óc Eo" ruins of Cattara in the Kingdom of Funan is located here and they are believed to be from a trading port dating to between the 1st and 7th centuries CE.

Thoại Sơn borders Châu Thành to the north, Tri Tôn to the west, Long Xuyên to the east and Kiên Giang province to the south.

This article about a location in An Giang province, Vietnam is a stub.