The Market Street Subway is a subway tunnel in San Francisco, California, United States. It runs under the length of Market Street and is used by both Muni Metro and BART. BART does not run through the entire subway; it turns to the south in its own tunnel before reaching Van Ness Avenue. In the section that BART does run in, there are tunnels on two levels for most of the length of the tunnel. The upper level is used by Muni Metro lines and the lower level is used by BART lines. The western end of the tunnel is connected to the Twin Peaks Tunnel and the eastern end on the BART level is connected to the Transbay Tube. Originally, all Muni Metro lines ended at the Embarcadero Station, but in 1998 a new exit to the tunnel past the station was opened. Only the N Judah line continues through this exit, with all other lines still terminate at the Embarcadero Station.

The K Ingleside, L Taraval, and M Oceanview Muni Metro lines run through the entire tunnel and into the Twin Peaks Tunnel. The J Church and N Judah lines leave the tunnel through an exit that connects to Church Street.

Stations on the Market Street Subway

There are a total of seven stations in the tunnel. Four are used by BART, five by all of the Muni Metro lines, and two by only three Metro lines:

• Embarcadero Station - J, K, L, M, and N Muni Metro lines, BART
• Montgomery Street Station - J, K, L, M, and N Muni Metro lines, BART
• Powell Street Station - J, K, L, M, and N Muni Metro lines, BART
• Civic Center Station - J, K, L, M, and N Muni Metro lines, BART
• Van Ness Station - J, K, L, M and N Muni Metro lines
• Church Street Station - K, L, and M Muni Metro lines (The J stops at the station above-ground and the N stops nearby)
• Castro Street Station - K, L, and M Muni Metro lines