William Frederick Sears (1868 – 23 March 1929) was an Irish Sinn Féin and later Cumann na nGaedheal politician. 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. 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. He was elected unopposed as a Sinn Féin Teachta Dála (TD) for the Mayo South–Roscommon South constituency at the 1921 elections.