Bang Yai (Thai: บางใหญ่, pronounced [bāːŋ jàj]) is a district (amphoe) in the western part of Nonthaburi province, central Thailand.

[1] Neighbouring districts are (from the north clockwise) Sai Noi, Bang Bua Thong, Mueang Nonthaburi, Bang Kruai, and Phutthamonthon of Nakhon Pathom province.

The district is divided into six sub-districts (tambons), which are further subdivided into 66 villages (mubans).

Since 2020 Bang Mae Nang has had town (thesaban mueang) status, covering most parts of tambon Bang Mae Nang.

Bang Yai as well as neighbouring Bang Kruai and Mueang Nonthaburi is the last natural habitat of the Alexandrine parakeet and red-breasted parakeet, a medium-sized parrot in Bangkok Metropolitan Region.