The Santa Monica Mountains National Recreation Area is a United States national recreation area containing many individual parks and open space preserves, located primarily in the Santa Monica Mountains of Southern California. The SMMNRA is in the greater Los Angeles region, with two thirds of the parklands in northwest Los Angeles County, and the remaining third, including a Simi Hills extension, in southeastern Ventura County.

A national recreation area (NRA) is a protected area in the United States established by an Act of Congress to preserve enhanced recreational opportunities in places with significant natural and scenic resources. There are 40 NRAs, which emphasize a variety of activities for visitors, including hiking, camping, boating, fishing, swimming, biking, horseback riding, and wildlife viewing, in areas that include multiple-use management for both conservation and limited utilization of natural resources. They have diverse features and contexts, being established around reservoirs, in urban areas, and within forests. Due to their size, diversity of activities, and proximity to population centers, NRAs are among the most visited units of the National Park System, with six among the thirty most visited sites.