State Highway 186 or SH 186 is a Texas state highway in deep south Texas from US 281 east to Port Mansfield.

SH 186 was designated by 1933 along a route from Linn to San Perlita. In 1973 the portion of SH 186 from San Perlita to south of San Perlita was transferred to FM 2209. In 1990, SH 186 was extended to Port Mansfield, replacing Farm to Market Road 497.