Relampago is a census-designated place (CDP) in Hidalgo County, Texas. The population was 132 at the 2010 United States Census. It is part of the McAllen–Edinburg–Mission Metropolitan Statistical Area.
The town was named for the Relampago Ranch, a rancho started in 1856 by José María Mora and Thaddeus Rhodes. Relámpago is Spanish for "lightning flash." The town for some years has been a first stop on the so-called ferrocarril subterráneo for migrants.