Fronteras is a city located in the northeastern region of the Mexican state of Sonora. It serves as the seat of the Fronteras Municipality and is situated at an elevation of 1,120 meters above sea level.
The name Fronteras translates to "Border" in English. The municipality covers a total area of 2,839.62 km², which accounts for approximately 1.53% of the state's total landmass. It is bordered by the municipalities of Agua Prieta, Nacozari, and Bacoachi.