A by-election was held in the Dáil Éireann Carlow–Kilkenny constituency in Ireland on 22 May 2015, to fill the vacancy left by the resignation of Fine Gael Teachta Dála (TD) Phil Hogan on his appointment as European Commissioner. It was held on the same day as national referendums on marriage equality and the age of eligibility for election to the office of president. The Electoral (Amendment) Act 2011 stipulates that a by-election in Ireland must be held within six months of a vacancy occurring. The by-election writ was moved in the Dáil on 29 April 2015.