William Byrd (circa 1540–1623) was an English composer.
William Byrd may also refer to:
- William Byrd I (1652–1704), Virginia colonist
- William Byrd II (1674–1744), colonial Virginia planter, author, and founder of Richmond
- William Byrd III (1728–1777), American racehorse owner
- William Byrd (baseball player) (1907–1991), American professional baseball player
- William Byrd Traxler Jr. (born 1948), federal judge on the U.S. Court of Appeals for the Fourth Circuit
- William Byrd, African-American man who was lynched in Brentwood, Georgia on May 28, 1922
- William A. Bird, often spelled Byrd, state legislator in Florida
- William M. Byrd (1819–1874), justice of the Supreme Court of Alabama