Interstate 605 (abbreviated I-605, officially known as the San Gabriel River Freeway and locally referred to as The 605) is a 27-mile-long (43 km) major north–south auxiliary Interstate Highway in the Greater Los Angeles urban area of Southern California. It runs from I-405 and State Route 22 (SR 22) in Seal Beach in Orange County to I-210 just south of the Irwindale–Duarte border in Los Angeles County. The San Gabriel River Freeway closely parallels the San Gabriel River for most of its alignment, hence its name, which is one of the few Southern California freeways not named after a city along its route.
Aside from changes to the interchange with I-105 (which did not open until the early 1990s), and the addition of an HOV lane between I-405 and I-10, I-605 is one of the only remaining freeways that kept its original alignment throughout its run through Los Angeles County since it first opened.