The Yokohama Municipal Subway 4000 series (横浜市交通局4000形) is a metro electric multiple unit (EMU) train type operated by the Yokohama City Transportation Bureau on the Yokohama Municipal Subway Blue Line in Japan since 2022.

[2] The trains use a VVVF traction control system that allows for full regenerative braking.

[3] On 13 December 2021, the Yokohama Municipal Subway announced that new trainsets would be purchased for the Blue Line, replacing the oldest 3000A series trainsets dating back to 1992.

[4] The order was originally made in 2018 for a new batch of 3000V series trainsets but that plan was abandoned in favour of newer 4000 series cars.

[5] As of 3 April 2022[update], five trainsets (30 vehicles) are to be commissioned in 2022 while the remaining three sets (18 vehicles) will enter service in 2023.