| Sir William Wilfred Sullivan | |
| Order: | 4th |
| Office: | Premier of Prince Edward Island |
| Predecessor: | Louis Henry Davies |
| Successor: | Neil McLeod |
| Lieutenant Governor: | Robert Hodgson Thomas Heath Haviland Andrew Archibald Macdonald Jedediah Slason Carvell |
| Term Start: | April 25, 1879 |
| Term End: | November 13, 1889 |
| Office1: | Leader of the Conservative Party of Prince Edward Island |
| Predecessor1: | Lemuel Owen |
| Successor1: | Neil McLeod |
| Term Start1: | 1877 |
| Term End1: | November 13, 1889 |
| Office2: | Chief Justice of Prince Edward Island |
| Predecessor2: | Edward Palmer |
| Successor2: | John Alexander Mathieson |
| Term Start2: | November 13, 1889 |
| Term End2: | June 21, 1917 |
| Office3: | Member of the General Assembly of Prince Edward Island for 2nd Kings |
| Predecessor3: | none |
| Successor3: | John P. Sullivan |
| Alongside3: | Hilary McIsaac, William Hooper, John Underhay |
| Term Start3: | 1872 |
| Term End3: | November 13, 1889 |
| Office4: | Administrator of Prince Edward Island |
| Predecessor4: | Jedediah Slason Carvell |
| Successor4: | George William Howlan |
| Term Start4: | February 14, 1894 |
| Term End4: | February 21, 1894 |
| Birth Date: | 6 December 1839 |
| Birth Place: | Hope River, Prince Edward Island Colony |
| Death Place: | Memramcook, New Brunswick, Dominion of Canada |
| Nationality: | Canadian |
| Party: | Conservative Party |
| Children: | 6 |
| Residence: | Charlottetown, Prince Edward Island |
| Alma Mater: | University of Prince Edward Island St. Dunstan's College |
| Occupation: | Journalist, lawyer, and judge |
| Profession: | Politician |
| Cabinet: | Solicitor General (1873–1876) |
Sir William Wilfred Sullivan (December 6, 1839 - September 30, 1920) was a Prince Edward Island journalist, politician and jurist, the fourth premier of Prince Edward Island.
A native of Hope River, Sullivan had a career as an assistant editor at the Charlottetown Herald as well as a lawyer before being elected to the provincial legislature in 1872 as a Liberal MLA.
A staunch Catholic, Sullivan became leader of the opposition in 1877 to the Protestant coalition government of Louis Henry Davies which had been formed to implement a public, secular school system that denied funding to Roman Catholic separate schools. Sullivan reorganised the Conservative Party and was asked by the lieutenant governor to become premier once Davies' coalition broke up and became unable to command a majority in the assembly.
Sullivan served as premier for ten years and fought for PEI's rights in Canada. He protested the federal government's failure to fulfill the terms of confederation on which the island had joined the dominion in 1873. In 1886, he petitioned the Imperial government in London protesting Canada's delinquency in respect to promises to ensure communication lines between the island and the rest of the country but the problem remained unresolved until the 1900s.
In 1889, Sullivan was appointed Chief Justice of PEI and served in that position until his retirement in 1917. In 1914 he was made a Knight Bachelor by King George V.