State Route 273 is a state highway in Shasta County, California, USA. The route takes a more direct approach to the cities of Anderson and Redding, passing through their downtown districts. Interstate 5 is a bypass of this route, as it connects both ends. This route was part of former U.S. Route 99.

In 2007 an effort was begun to have this segment signed as "Historic Route 99". Supporters hope to have black-and-white historical Route 99 signs up by October. They will be placed from North Market Street in Redding down to where Interstate 5 meets Highway 273 south of Anderson.

SR 273 begins just south of Anderson at an interchange with Interstate 5. The roadway then parallels I-5 northeast into central Anderson. Upon exiting a suburban area, the route enters farmland, while paralleling the Sacramento River. The roadway then enters suburban Redding, where it turns away from the Sacramento River and zigzags along local roads through downtown, where it meets State Route 299. Upon exiting downtown, SR 273 crosses the Sacramento River and meets its northern terminus at Interstate 5 in the suburbs of Redding.

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 Shasta County.