The 1918 East Tyrone by-election was held on 3 April 1918. The by-election was held due to the resignation of the incumbent Irish Parliamentary Party MP, William Redmond. It was won by the Irish Parliamentary candidate Thomas Harbison.^[1]

Redmond had resigned in order to contest the Waterford City by-election which had become vacant when his father, John Redmond, had died. The Sinn Féin candidate was Seán Milroy. The by-election was the last in a short string of by-elections where it seemed that the more moderate nationalists were regaining ground from Sinn Féin before being virtually wiped out in the 1918 Irish general election.