Bang Kruai (Thai: บางกรวย, pronounced [bāːŋ krūa̯j]) is a district (amphoe) in the southern part of Nonthaburi province, central Thailand.

Due to its size it was difficult to administer, and thus in 1917 the northern part was split off as minor district (king amphoe), Bang Mae Nang.

The district is divided into nine sub-districts (tambons), which are further subdivided into 60 villages (mubans).

Since 2002 Bang Kruai itself has had town (thesaban mueang) status.

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