The Bay Lights, LED light installation on the Bay Bridge in San Francisco, United States

The Bay Lights is a light sculpture on the western span of the San Francisco–Oakland Bay Bridge, between Yerba Buena Island and San Francisco. It consists of 25,000 white LEDs spaced every 12 inches along 1.8 miles of the vertical steel support cables on the north side of the suspension span. The lights are attached with 60,000 zip ties and controlled by a computer program that creates abstract patterns ascending and descending the cables.

Conceived in September 2010 by Ben Davis of Words Pictures Ideas, the project was created by light artist Leo Villareal and opened on March 5, 2013, for the Bay Bridge's 75th anniversary. The temporary installation came down in March 2015 when its permits expired so Caltrans could repaint the cables; more robust permanent lights were re-lit on January 30, 2016. The lights went dark on March 5, 2023, and were switched on again at a ceremony on March 20, 2026.

The work was conceived by Ben Davis of the public relations firm Words Pictures Ideas, who felt the Bay Bridge stood in the shadow of the Golden Gate Bridge as a tourist destination. He brought in light artist Leo Villareal, whose patterns were inspired by water, traffic and local weather; both cite Burning Man as an influence.

The lights sit on the north side of the western span, so they are seen from San Francisco's waterfront, not from the bridge roadway; they were placed to stay out of drivers' sight. They run from dusk until dawn daily. The permanent fixtures installed in 2016 are angled to be visible from south of the bridge as well.

The lights follow computer algorithms designed to ensure the pattern never repeats, meaning each night produces a completely fresh sequence of illuminations. This means every visitor sees a different light show depending on when they watch the bridge.