William O'Sullivan

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 (born 1968), Irish hurler
 * Billy O'Sullivan (footballer) (born 1959), English former footballer