Marysville is a city in and the county seat of Yuba County, California, United States, located at the confluence of two rivers which drain the watersheds containing the most productive gold mining region in Northern California. As the depot for the Northern mines it became an important early center of commerce, growing into one of the largest cities in California's first decade of existence, before the gold was all mined. It is one of only 2 cities in California named after a woman who is not a Catholic saint, after a survivor of the Donner Party, which lost half of the people to starvation in the Sierra Nevada during the winter of 1846–47.
As of the 2010 United States Census, the population was 12,072, reflecting a decrease of 196 from the 12,268 counted in the 2000 Census. It is included in the Yuba City Metropolitan Statistical Area, often referred to as the Yuba–Sutter area after the two counties, Yuba and Sutter. The metropolitan statistical area is part of the Greater Sacramento area.