This is a list of by-elections to Dáil Éireann, the house of representatives of the Oireachtas, the Irish legislature. By-elections in Ireland occur to fill vacant seats which can be caused by the death, resignation, disqualification or expulsion of a sitting Teachta Dála (member of parliament). Under the Electoral (Amendment) Act 2011, the writ for the by-election must be issued within six months of the vacancy. Twenty-three TDs who were elected at a by-election were not subsequently re-elected at a general election. The only person twice elected at by-elections was Thomas Hennessy.