Hat Yai (Thai: หาดใหญ่, pronounced [hàːt jàj]) is a district (amphoe) of Songkhla province, southern Thailand.

Neighboring districts are (from the west clockwise): Khuan Kalong of Satun province; Rattaphum, Bang Klam, Khuan Niang, Singhanakhon, Mueang Songkhla, Na Mom, Chana, Na Thawi, Sadao, and Khlong Hoi Khong.

The district is divided into 13 sub-districts (tambons), which are further subdivided into 98 villages (mubans).

There are four towns (thesaban mueang): Ban Phru covers parts of tambon Ban Phru, and Khlong Hae, Khuan Lang and Kho Hong each cover tambons of the same names.

Missing numbers are tambons which now form districts Bang Klam and Khlong Hoi Khong.