Others
- William C. Sullivan (1912–1977), United States security official
- William H. Sullivan (born 1922), United States diplomat
- William J. Sullivan, American judge on the Connecticut Supreme Court
- William John Sullivan (born 1976), software freedom activist, hacker and writer
- William Laurence Sullivan (1872–1935), Unitarian clergyman and author
- Billy L. Sullivan (born 1980), American actor
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