William O'Sullivan may refer to:
William S. O'Sullivan (1928–1971), Irish-American loanshark and mob enforcer William O'Sullivan (politician), Irish Cumann na nGaedheal politician William Henry O'Sullivan (1829–1887), Irish Home Rule League politician Billy O'Sullivan (footballer) (born 1959), English former footballer
See also
Billy O'Sullivan (disambiguation) William Sullivan (disambiguation)