Omnitrans, stylized as "OmniTrans," is a public transportation agency in San Bernardino County, California, United States. The largest transit operator within San Bernardino County, it serves the San Bernardino Valley. The agency was established in 1976 through a joint powers agreement and today includes 15 cities and portions of the unincorporated areas of San Bernardino County. In addition to the southwestern corner of San Bernardino County, Omnitrans provides service to parts of Riverside and Los Angeles Counties. Omnitrans currently carries about 11 million passengers per year. Omnitrans currently operates fixed route bus service, bus rapid transit and a paratransit service for the disabled, “Access.” Omnitrans operates throughout the urbanized area of southwestern San Bernardino County: south of the San Bernardino Mountains, from Upland, Montclair, and Chino in the west to Redlands, California and Yucaipa in the east. The Omnitrans service area covers approximately 480 square miles (1,200 km2).

The San Bernardino Valley is a valley in Southern California located at the south base of the Transverse Ranges. It is bordered on the north by the eastern San Gabriel Mountains and the San Bernardino Mountains; on the east by the San Jacinto Mountains; on the south by the Temescal Mountains and Santa Ana Mountains; and on the west by the Pomona Valley. Elevation varies from 590 feet (180 m) on valley floors near Chino to 1,380 feet (420 m) near San Bernardino and Redlands. The valley floor is home to over 80% of the more than 4 million people in the Inland Empire region.