Avenue B and C or B&C Colonia is a census-designated place (CDP) and colonia in Yuma County, Arizona, United States. The population was 4,176 at the 2010 census. Areas that are part of Avenue B and C were first subdivided in the 1920s and 1930s. The colonia received a sewer system in 2011. It is the fifth most populous community in Yuma County and second most populous CDP (behind Fortuna Foothills).