The K Ingleside is a light rail line of the Muni Metro system in San Francisco, California.

Surface stations are typically boarding islands located between the tracks and the outer traffic lanes.

The K Ingleside runs through the Twin Peaks Tunnel and Market Street subway to its inner terminal at Embarcadero station.

[5] The line was extended to the Ingleside House (where Ocean Avenue now meets Junipero Serra Boulevard) shortly thereafter.

[7] The San Francisco Municipal Railway (Muni) opened its K line along with the Twin Peaks Tunnel on February 3, 1918.

On June 1, 1918, the J and K lines were removed from Van Ness Avenue and extended along Market Street to a loop at the Ferry Building.

[7] The existing URR streetcar service on Ocean Avenue formed a barrier to continued Muni expansion into the Ingleside district.

[7] Muni bought the Market Street Railway (ex-URR) in 1944; route 12 service was removed from Ocean Avenue on April 8, 1945, leaving just the K Ingleside.

[8]: 186  Service past the loop to Mission ended on October 10, 1952, although trackage as far as San Jose Avenue was kept for non-revenue moves to the carhouse.

The Muni tracks and overhead power system were replaced, boarding islands were reconstructed, and accessible platforms built at Ocean and Lee.

[19] K Ingleside light-rail service was replaced again by the K Bus on August 25, 2020 due to issues with malfunctioning overhead wire splices and the need to quarantine control center staff after a positive COVID-19 case.

[21] On January 7, 2023, the T Third Street line was rerouted into the Central Subway ending 16 years of being interlined with the K Ingleside, which resumed terminating at Embarcadero.

[23] In 2023, the SFMTA began planning work on the K Ingleside Rapid Project, which was intended to increase capacity and reduce travel time on the Ocean Avenue portion of the line.

At that time, the second car began staying open to passengers as far as Ocean Avenue/CCSF Pedestrian Bridge on Balboa Park-bound trains.