Interstate 215 (I-215) is a 54.5-mile (87.7 km) long north–south Interstate highway in the Inland Empire region of Southern California. It is an auxiliary route of Interstate 15 (I-15), running from Murrieta to northern San Bernardino. While I-215 connects the city centers of both Riverside and San Bernardino, its parent I-15 runs to the west through Ontario.

Part of I-215 was originally built and signed as Interstate 15E, but this was later changed as almost all of the Interstates around the country with directional suffixes were eventually renumbered or eliminated, sans I-35E and I-35W in Texas and Minnesota.

I-215 is part of the California Freeway and Expressway System and is eligible for the State Scenic Highway System.

The southern terminus of Interstate 215 is at the junction of Interstate 15 in the city of Murrieta in southern Riverside County. It then runs north through Perris before joining State Route 60 in Moreno Valley.

I-215 splits from SR 60 at State Route 91 in Riverside, where it then travels to San Bernardino before terminating at I-15 near the small San Bernardino neighborhood of Devore.

This route is an alternative to I-15 for drivers traveling from, for example, Phoenix, Las Vegas, Nevada, and San Bernardino, to the San Diego metropolitan area. This route offers more of a distance advantage since it is an alternative to Interstate 15's alignment that is about 10 miles (16 km) to the west of, and roughly parallel to, I-215. However, the traffic and time "advantage" on I-215 is limited by three factors: the segment between the I-15 / I-215 "Devore junction" and San Bernardino only has two lanes in each direction (on the other hand, I-15 has four), it is co-signed with SR 60 between Riverside and Moreno Valley, and it has only two lanes in each direction between Perris and Menifee.

I-215 is also used by local residents as the major north–south route for the urbanized portions of the San Bernardino-Riverside-Ontario Metropolitan Area. (I-15 serves a similar function in the western portion of the metropolitan area; the two are the only continuous north–south freeways in the area.)

Interstate 215 is named the Escondido Freeway from its southern terminus in Murrieta to SR 60 in Moreno Valley. From that point to SR 91, I-215 is co-signed with SR 60 where it inherits the Moreno Valley Freeway name. Between the SR 60/SR 91 interchange in Riverside to Interstate 10 in San Bernardino, the highway is known as the Riverside Freeway. Between I-10 and State Route 210, I-215 is named the San Bernardino Freeway. From SR 210 to its northern terminus, I-215 is named the Barstow Freeway.

On January 24, 1957, the State Highway Commission defined the Escondido Freeway as what is now Routes 15 and 215 from Route 805 to Route 91. This entire segment was previously Route 395 when it was named. Since then, the definition was extended on Route 15 south to Route 8 by Assembly Concurrent Resolution 34, Chapter 67 in 1979. Meanwhile, the segment of Route 15 from the San Diego County Line to the I-15/I-215 interchange was named the Temecula Valley Freeway in 1990.

The highway (not an Interstate) that is currently Interstate 215 first opened in 1963 as part of U.S. Route 395. The "mileposts" in Riverside County reflect this, since they do not go to zero at the Interstate 15 interchange in Murrieta. In circa 1968, U.S.395 was renumbered as I-15 (the original proposed route, as CA 71's proposed number was I-15W/CA 31 Hamner-Milliken). This segment of US 395 was again renumbered in 1972 as (Temporary) Interstate 15E. Next in 1982, this route was renumbered as I-215 north of CA 60, and as State Route 215 south of State Route 60. Once State Route 215 was upgraded by construction to Interstate Highway standards, it became part of I-215 in 1994. Prior to its upgrade to Interstate Standards, there were traffic signals at CA 74 junction, as well as at Allesandro (in Moreno Valley); rail road crossing also intersected the expressway at CA 74 .

Due to the fact that the I-215 designation was overlaid upon existing freeways between the southern junction with SR 60 and the city of San Bernardino, the SR 60/SR 91/I-215 interchange in the city of Riverside has been widely known for its confusing nature concerning the numbering of I-215. While SR 60 continues east-and-west through this interchange, and SR 91 continues south (and formerly to the north, the number having now been removed), the I-215 designation continues away from this interchange on SR 60 East and the former northern portion of SR 91 (now solely numbered I-215). Travelers following I-215 in either direction need to "change freeways" at this interchange, instead of just following through lanes. The interchange was recently reconstructed to include some high-speed flyovers, one of which carries I-215 southbound traffic.

A joint project between Caltrans and SANBAG of San Bernardino County to widen I-215 between Orange Show Road and University Parkway in San Bernardino began in 2007. Upon completion, the project will add one general use lane and one carpool lane in each direction, bringing the total number of lanes from six to 10 lanes across. The 7.5-mile, $723 million project includes the reconstruction of all underpasses and overpasses within the project as well as connector ramps between I-215 and SR-210. The project has four phases with three of the four already complete. This major expansion and revitalization project will help reduce congestion and improve traffic flow on this freeway that serves as a gateway to Victor Valley, Riverside County, Orange County, Los Angeles County and points beyond. The end of construction is expected in 2013.

Phase 1 Status: Complete

Reconstruction of 5th Street Bridge. Work began in January 2007 and was completed in November 2008, approximately six months ahead of schedule and $2 million under budget. The 5th Street bridge was built in phases with the new bridge being constructed alongside the old structure to allow for continuous use of the east/west corridor during construction.

Phase 2 Status: Complete

Freeway Widening Between Orange Show Road and Rialto Avenue. Construction began on Phase 2 in December 2007 and was completed in July 2010. In addition to the reconstruction of various bridges, the freeway was widened from three to five lanes in each direction through this stretch of road. Aesthetic wallscapes depict the City’s iconic symbols including palm trees, the San Bernardino mountain range, fountains representing the local springs and more.

Phase 3 Status: Underway

Freeway Widening Between Rialto Avenue to Massachusetts Avenue. Construction began in September 2009 and is expected to be complete mid-2013. This phase received $128 million in American Recovery and Reinvestment Act of 2009 (ARRA) funds, one of the largest allocations of funding to a construction project in the country. As part of this phase, freeway lanes will be widened from three to five lanes in each direction along with the reconstruction of various bridges and underpasses. Following construction completion, all fast-lane entrances and exits will be eliminated with drivers using new 5th Street and Baseline Street on-ramps that connect directly to the newly constructed bridges. This new configuration will provide more balanced access to the west and east sides of the city. What’s more, residents living alongside the northbound side of the freeway will have a soundwall to help block the freeway noise.

Phase 4 Status: Complete

Freeway Widening Between Massachusetts Avenue and University Parkway. Construction began in January 2010 and was completed in November 2012. A key feature in this phase was the construction of I-215/SR-210 connector ramps. Drivers now have direct access to these freeways in all directions. In addition to a general use and carpool lane added in each direction south of the I-215/SR-210 interchange, a southbound auxiliary lane and a northbound general use lane have been added between University Parkway and the I-215/SR-210 interchange.

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 numbers reset at county lines; the start and end postmiles in each county are given in the county column.