The Osaka Metro 400 series is an electric multiple unit (EMU) train type built by Hitachi Rail for Osaka Metro. Entering service on 25 June 2023, a total of 23 six-car sets are to be built.

The Osaka Metro is a major rapid transit system in the Osaka Metropolitan Area of Japan, operated by the Osaka Metro Company, Ltd. It serves the city of Osaka and the adjacent municipalities of Higashiosaka, Kadoma, Moriguchi, Sakai, Suita, and Yao. Osaka Metro forms an integral part of the extensive mass transit system of Greater Osaka, having 123 out of the 1,108 rail stations (2007) in the Osaka-Kobe-Kyoto region. In 2010, the greater Osaka region had 13 million rail passengers daily of which the Osaka Municipal Subway accounted for 2.29 million.