Born in Houston, Cornyn is a graduate of Trinity University and St. Mary's University School of Law, and received an LL.M. degree from the University of Virginia School of Law. He was a judge on Texas's 37th District Court from 1985 to 1991. He was elected an associate justice of the Texas Supreme Court, where he served from 1991 to 1997. In 1998, Cornyn was elected Attorney General of Texas, serving one term until winning a seat in the U.S. Senate in 2002. He has been reelected three times in 2008, 2014, and 2020.