Yokohama Municipal Subway Green Line

The Yokohama Municipal Subway Green Line (横浜市営地下鉄グリーンライン) is a rapid transit line serving Yokohama in Kanagawa Prefecture, Japan. It is the shorter of the two lines in the Yokohama Municipal Subway system operated by Yokohama City Transportation Bureau. Its formal designation is Line 4, and it is the first section to be opened of a proposed Yokohama Circular Railway (横浜環状鉄道).

The Green Line links Nakayama on the JR East Yokohama Line and Hiyoshi on the Tokyu Toyoko Line with 13.0 km of track and 10 stations. Construction began in 2001 and the new line started operating on 30 March 2008. It uses linear motor propulsion and a full journey takes approximately 21 minutes one way.

Stations
Platforms are above ground at Kawawachō, Center-Kita, and Center-Minami stations and underground at other stations.

Rolling stock
The Green Line is operated by 17 4-car 10000 series EMUs. In 2018, it was announced that 10 of these would be lengthened to six cars each by 2024 as a measure to ease overcrowding on the Green Line. By April 2023, lengthening of 4-car trains to 6-car trains had commenced, and by the end of fiscal year 2024, there will be 10 x 6-car trains.