William Barclay may refer to:
- William Barclay (jurist) (1546–1608), Scottish jurist
- William Barclay (writer) (c. 1570–c. 1630), Scottish writer
- William Barclay (painter) (1797–1859), English miniature painter
- William Barclay (theologian) (1907–1978), theologian and writer of Bible commentaries
- William Barclay (New York politician) (born 1969), New York State Assemblyman
- William Barclay (Northern Ireland politician) (1873–1945), Northern Irish Senator
- William Edward Barclay (1857–1917), football manager of Everton and of Liverpool
- Bill Barclay (died 2001), American athlete and coach