The Frio River rises from the juncture of the East, West, and Dry Frio rivers (at 29°44′ N, 99°45′ W) and flows southeast, across central Uvalde and Frio counties and northeastern LaSalle, northern McMullen, and northwestern Live Oak counties, for 200 miles to its mouth on the Nueces River, a mile south of Three Rivers (at 28°26′ N, 98°11′ W).
It is joined by the Leona River in southern Frio County, the Sabinal River in southeastern Uvalde County, and the Atascosa River two miles north of Three Rivers in Live Oak County. Other tributaries include Hackberry, Cibolo, Hondo, and Live Oak creeks and Big Slough.
The Frio River runs east of Uvalde, Texas, and west of Pearsall, through Leakey, Texas, Knippa, and Concan, Texas. Downstream it runs through Fowlerton, Tilden, and Three Rivers. It is dammed to form the Corder, Frank Kincaid, Miller, Garwood, V-Bar, Sirianni, Tips, and Diamond Shamrock lakes and the Burns, Bennett, and Choke Canyon reservoirs. Frio is Spanish for “cold.” The river’s drainage area is 7,310 square miles. It has been identified as the stream that Alonso De Leónqv called Rio Sarco in 1689.