State Route 54 (SR 54) is a California State Highway in San Diego that connects Interstate 5 to the city of El Cajon. The first section was built circa 1961, and the final section of freeway (which was upgraded from an expressway) opened in 2007.

This route is part of the California Freeway and Expressway System. Route 54 has the three different names given by various state laws. These names include Jamacha Road (from Campo Road to East Main Street in El Cajon), South Bay Freeway (from I-805 to Route 94) and Filipino-American Highway (from its western terminus to Route 125). The freeway portion of Route 54 is commonly referred to as the South Bay Freeway, and the roadway segments are commonly referred to by their respective names (Jamacha Boulevard, Campo Road, and Jamacha Road).

Route 54 starts as a freeway from Interstate 5 at the mouth of the Sweetwater River, with westbound traffic traversing the north bank of the river and eastbound traffic traversing the south bank. Both sides join near the junction with Interstate 805 and continue east for several miles. As the freeway turns north, it becomes Route 125 and Route 54 exits at Jamacha Boulevard.

Route 54 follows Jamacha Boulevard northeast until reaching Campo Road. The portion of Route 54 along this arterial road is shared with San Diego County Route S17 and historically has been signed for S17 only.

Route 54 then shares a brief concurrency with Route 94, although this is not documented in the legal definition of either route, following Campo Road 0.5 miles east. Route 54 continues northeast on Jamacha Road to El Cajon, while Campo Road (Route 94) splits off to the southeast. Route 54 currently ends at the El Cajon city limit.

Route 54 first opened between Sweetwater Road (at the site of present day North 2nd Avenue in Chula Vista) and Jamacha Boulevard in Spring Valley. The South Bay Freeway was constructed as a freeway only between its western terminus and Reo Drive, a short distance west and east of the I-805 junction, with the remainder built as an expressway.

Route 54 was extended west as a freeway to I-5 at the same time the Sweetwater River flood control channel was constructed in the early 1990s. The expressway portion from Reo Drive to South Worthington Street was upgraded to a freeway in the late 1990s, and a part-time HOV lane opened in each direction, east of I-805 only, around this time.

The State relinquished Route 54, from the southern El Cajon city limit to I-8 only, to the City of El Cajon in 1999. The portion of Route 54 within El Cajon was then incorrectly designated Interstate Business Route 54 by the City, but most business route signage has since been removed.

The remaining expressway portion of Route 54, running from South Worthington Street to Jamacha Boulevard, was replaced by a freeway in two phases in the 2000s. The first phase corresponded with construction of Route 125 north of Jamacha Boulevard and was completed in 2003. The second phase corresponded with construction of the South Bay Expressway toll road and was completed in 2007. The HOV lanes were converted to regular mixed traffic lanes shortly thereafter.

Except where prefixed with a letter, postmiles were measured on the road as it was in 1964, and do not necessarily reflect current mileage. The entire route is in San Diego County.