District 21 of the Texas Senate is a senatorial district that currently serves all of Caldwell, Dimmit, Duval, Jim Hogg, Karnes, La Salle, Live Oak, McMullen, Starr, Webb, Wilson, and Zapata counties and portions of Bexar, Guadalupe, Hays, Travis counties in the U.S. state of Texas.

[1] The current senator from District 21 is Judith Zaffirini.

District 21 has a population of 807,460 with 567,099 that is at voting age from the 2010 census.

[2] Election history of District 21 from 1992.

[b]