Trolleybuses in San Francisco

The San Francisco trolleybus system forms part of the public transportation network serving San Francisco, in the state of California, United States. Opened on October 6, 1935, it presently comprises 15 lines and is operated by the San Francisco Municipal Railway, commonly known as Muni (or the Muni), with around 300 trolleybuses. In San Francisco, these vehicles are also known as "trolley coaches", a term that was the most common name for trolleybuses in the United States in the middle decades of the 20th century. In 2024, the system had a ridership of 48,114,500, or about 140,300 per weekday as of the first quarter of 2025.

The Muni trolleybus system is complementary to the city-owned Muni bus services, Muni Metro and cable car system and the rail-bound regional Caltrain and Bay Area Rapid Transit systems. In addition, it shares some of its overhead wires with the F Market & Wharves streetcar line.

One of only four such systems currently operating in the U.S., the Muni trolleybus system is the second-largest such system in the Western Hemisphere, after that of Mexico City. The system includes the single steepest known grade on any existing trolleybus line in the world (22.8% in the block of Noe Street between Cesar Chavez Street and 26th Street on route 24 Divisadero), and several other sections of Muni trolleybus routes are among the world's steepest.