Tubac is a census-designated place (CDP) in Santa Cruz County, Arizona, United States. The population was 949 at the 2000 census. The place name Tubac is an English borrowing from a Hispanicized form of the O odham name, which translates into English as rotten. The original odham name is written Cuwak, remembering that the initial syllable is accented. When first taken into Spanish speech, it was spelled Tubaca. Finally over time the last a was dropped. Tubac is situated on the Santa Cruz River.