Tubac is a census-designated place in Santa Cruz County, Arizona, United States. The population was 1,191 at the 2010 census. The place name "Tubac" is an English borrowing from a Hispanicized form of the O'odham name Cuwak, which translates into English as "place of dark water". When first taken into Spanish speech, it was spelled Tubaca. Finally, over time, the latter "a" was dropped. Tubac is situated on the Santa Cruz River. Tubac was the original Spanish colonial garrison in Arizona.