Bang Pa-in (Thai: บางปะอิน, pronounced [bāːŋ pā.ʔīn]) is one of the 16 districts (amphoe) of Phra Nakhon Si Ayutthaya province, central Thailand.

Bang Pa-in was established in the Ayutthaya era in the name Khwaeng Uthai.

In 1910 Khwaeng Uthai Noi was changed status and renamed to Phra Ratchawang District.

Its name Bang Pa-in is believed to be distorted from Bang Phra In (บางพระอินทร์), literally meaning "place of Indra", refers to place of Inthraracha, the title of Songtham before became the king.

[2] The historic building Bang Pa-in Royal Palace was built during the Prasat Thong's reign, which was believed that he was a cousin to Songtham.