The Cuyama River is a river in southern San Luis Obispo County and northern Santa Barbara County, California. The 85-miles river is a tributary of the Santa Maria River, which is formed when the Cuyama River meets the Sisquoc River. Its upper reaches are in Ventura County, where it is split into a north and south fork. After the forks combine, the river briefly flows through the far northeast through the towns of Cuyama and New Cuyama in Santa Barbara County before entering San Luis Obispo County, California. The river travels just inside San Luis Obispo County for most of its length, a couple of miles above Santa Barbara County. When it becomes the Santa Maria River, it serves as the boundary between the two counties.