Rillito is a census-designated place in Pima County, Arizona, United States, surrounded by the town of Marana. The largest business in the community is Arizona Portland Cement and the community has had a post office since the 1920s. There is a regional park and recreation center in the middle of the community. Rillito has the ZIP Code of 85654; in 2000, the population of the 85654 ZIP Code Tabulation Area was 148.