State Route 91 (SR 91) is a major east–west state highway in the U.S. state of California that serves several regions of the Greater Los Angeles urban area. A freeway throughout its entire length, it officially runs from Vermont Avenue in Gardena, just west of the junction with the Harbor Freeway, east to Riverside at the junction with the Pomona and Moreno Valley freeways.

Vermont Avenue is one of the longest running north–south streets in City of Los Angeles and Los Angeles County, California. With a length of 23.3 miles (37.5 km), is the third longest of the north–south thoroughfares in the region. For most of its length between its southern end in San Pedro and south of Downtown Los Angeles, it runs parallel to the west of the Harbor Freeway (I-110).