Big Blue Bus is a public transit agency that provides public bus services for the city of Santa Monica and the greater Westside region of Los Angeles County, California. The service, operated by the city of Santa Monica, was founded on April 14, 1928 and throughout its existence has used a blue color scheme for its buses, leading to the Big Blue Bus nickname that would later become the official name of the agency. In 2023, the system had a ridership of 8,289,600, or about 29,900 per weekday as of the fourth quarter of 2023. Big Blue Bus receives funding from the Los Angeles County Metropolitan Transportation Authority (Metro) and offers connections to its Metro Bus and Metro Rail systems, but is operated independently from Metro.

Santa Monica is a city in Los Angeles County, situated along Santa Monica Bay on California's South Coast. Santa Monica's 2020 U.S. Census population was 93,076. Santa Monica is a popular resort town, owing to its climate, beaches, and hospitality industry. It has a diverse economy, hosting headquarters of companies such as Hulu, Activision Blizzard, Universal Music Group, Lionsgate, Illumination and The Recording Academy.