William Frederick Sears (1868 – 23 March 1929) was an Irish Sinn Féin and later Cumann na nGaedheal politician.^[1][2]

Sears was born in Neale, County Mayo in 1868. He was elected as a Sinn Féin MP for the Mayo South constituency at the 1918 general election.^[3] In January 1919, Sinn Féin MPs refused to recognise the Parliament of the United Kingdom and instead assembled at the Mansion House in Dublin as a revolutionary parliament called Dáil Éireann, though Sears did not attend as he was in prison.^[4] He was elected unopposed as a Sinn Féin Teachta Dála (TD) for the Mayo South–Roscommon South constituency at the 1921 elections.

He supported the Anglo-Irish Treaty and voted for it. He was re-elected unopposed for the same constituency at the 1922 general election, this time as a pro-Treaty Sinn Féin TD. He was elected as a Cumann na nGaedheal TD for Mayo South constituency at the 1923 general election.^[5] He lost his seat at the June 1927 general election but was elected to the Seanad in 1928. He died in office in 1929 and the by-election for his seat was won by Sir Nugent Everard.

In 1902 he founded the Enniscorthy Echo in co-operation with Sir Thomas Esmonde.^[1]