William Seymour may refer to:
- William Seymour (MP for Herefordshire) (died 1391), MP for Herefordshire (UK Parliament constituency)
- William Digby Seymour (1805–1872), MP for Kingston-upon-Hull
- William Digby Seymour, QC, lawyer and poet, MP for Sunderland and Somerset
- William H. Seymour (1840–1913), American politician
- William J. Seymour (1870–1922), American Pentecostal minister
- William Kean Seymour (1887–1975), British writer
- William Seymour (Congressman) (c. 1780–1848), US Representative from New York from 1835–1837.
- William Seymour (soldier) (1664–1728), Lieutenant-General, MP for Cockermouth, Totnes and Newport (Isle of Wight)
- William Seymour, 2nd Duke of Somerset (1588–1660)
- William Seymour, 3rd Duke of Somerset (1654–1671)
- William Seymour Tyler (1810–1897), American historian