Bang Kruai is a district (amphoe) in the southern part of Nonthaburi Province, central Thailand.The district was created in 1904 and named Bang Yai. 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. In 1921 Bang Mae Nang became a full district.On 19 October 1930 the district was renamed "Bang Kruai", after the geographic shape of district. "Kruai" is the Thai word for "cone". On the same date Bang Mae Nang received the old name of the district, "Bang Yai". Neighboring districts are (from north clockwise) Bang Yai, Mueang Nonthaburi, the districts Bang Sue, Bang Phlat, Taling Chan, Thawi Watthana of Bangkok, and finally Phutthamonthon (Nakhon Pathom Province).