Mile Square Regional Park, Regional park in Fountain Valley, California.

Mile Square Regional Park is a regional park in Fountain Valley, California, occupying a one-square-mile square bounded by Edinger and Warner Avenues and Brookhurst and Euclid Streets. It holds two lakes, two 18-hole golf courses, an archery range, baseball and softball fields, picnic shelters, a 20-acre urban nature area of California native plants, and a 55-acre recreation center with tennis, basketball and racquetball courts.

The park originated in 1942 when the U.S. Navy acquired 640 acres of farmland for Naval Air Station Los Alamitos. The site initially served as a training facility for carrier aircraft operations.

The park offers spaces for community gatherings with multiple picnic areas and sports facilities. A section is dedicated to California native plants and demonstrates the natural vegetation of the region.

The grounds are easily accessible by car and feature parking for visitors. The best time to visit is in the morning or late afternoon when the sun is lower and temperatures are more comfortable.

The grounds contain three landing fields arranged in a triangle formation, each originally used for carrier deck training. This unusual layout is a remnant of its time as a naval base and remains visible in how the park is organized today.