Frank Ray Keyser Sr. (September 29, 1898 – March 7, 2001) was an American politician, lawyer, and judge from Vermont. He was a lawyer in private practice and later a justice of the Vermont Supreme Court. His son F. Ray Keyser Jr. served as Speaker of the Vermont House of Representatives and later as governor of Vermont.
Keyser was born on September 29, 1898, in Woodsville, New Hampshire, to Winifred S. and Harriett (Bailey) Keyser.
He graduated from high school in Woodsville in 1917 and studied at Tufts University while enrolled in the Student Army Training Corps during World War I. After being discharged, he attended Norwich University, and became a banker in Wells River, Chelsea and Lyndonville, Vermont, and then a schoolteacher in Chelsea. Keyser read law part-time with Stanley C. Wilson. Admitted to the bar in 1929, he was a law partner in Chelsea with Wilson, Deane C. Davis, and J. Ward Carver. This distinguished group included two future governors (Wilson and Davis), one future Vermont attorney general (Carver), and one future state supreme court justice (Keyser).
Keyser held many local offices, serving as school director, selectman, town moderator, auditor, tax collector, town counsel, and fire district committee member. He was elected in 1937 and 1939 to the Vermont House of Representatives. Keyser also served as Orange County State's Attorney, Secretary of Civil and Military Affairs (chief assistant) to Governor Lee E. Emerson, and (during World War II) chief enforcement officer for the federal Office of Price Administration. Keyser served as president of the Vermont Bar Association, and was a member of the local American Legion post and Masonic lodge.