John Harris Whitmire (born August 13, 1949) is an American attorney and politician who is the longest-serving current member of the Texas State Senate. Since 1983, he has represented District 15, which includes much of northern Houston, Texas. His tenure earns him the title of Dean of the Senate. Previously he was a member of the Texas House of Representatives from 1973 through 1982. He also served as the Acting Governor of Texas in 1993 as part of the Governor for A Day tradition.