U.S. Route 181

U.S. Route 181
US 181 highlighted in red
Route information
Auxiliary route of US 81
Length	136.76 mi[1] (220.09 km)
Existed	1927[1]–present
Major junctions
South end	I-37 / SH 35 at Corpus Christi
Major intersections	Future I-69E / US 77 in Sinton Future I-69W / US 59 in Beeville
North end	I-37 near San Antonio
Location
Country	United States
Counties	Nueces, San Patricio, Bee, Karnes, Wilson, Bexar
Highway system
United States Numbered Highway System List Special Divided

U.S. Highway 181 is a south–north U.S. Highway located entirely in the state of Texas. Both termini are at Interstate 37, the road that it mainly parallels to the east. US 181 begins in Corpus Christi, Texas at mile marker 0^{[citation needed]} to the south, through south-central Texas to just south of San Antonio to the north (mile marker 131), for a total length of 137 miles (220 km).^[1]

The highway's northern terminus is at an intersection with Interstate 37 one mile (1.6 km) south of San Antonio's Interstate 410 loop, about 12 miles (19 km) northwest of Floresville. Prior to the Interstate era, US 181 traveled into Downtown San Antonio along Presa St. to an intersection with its parent route, US 81, which then ran along Alamo St.

Its southern terminus is in Corpus Christi, Texas at Interstate 37 near the Gulf of Mexico. I-37 and US 181 have mutual termini, such that traffic traveling southbound on I-37 will automatically merge onto northbound US 181, and vice versa.