Prachuap Bay (Thai: อ่าวประจวบ, RTGS: Ao Prachuap, pronounced [ʔàːw prā.tɕùap]) is a bay in the west side of the Gulf of Siam or Gulf of Thailand.

[1] It lies off Prachuap Khiri Khan town, Prachuap Khiri Khan Province.

It is open towards the east and is bound by steep limestone outcrops forming peninsulas to the north, at Khao Ta Mong Lai and to the south at Khao Lom Muak.

[3] Ko Lak Island in Prachuap Bay was the historic center of administration of Prachuap Khiri Khan Province and its silhouette appears on the provincial seal.

This Thailand location article is a stub.