Irish Finance Minister Brian Cowen was elected prime minister in an 88-76 parliamentary vote. His predecessor, Bertie Ahern, stepped down Tuesday after 11 years in power.
Cowen, 48, immediately reshuffled the Cabinet, appointing new ministers of finance, justice, foreign affairs and several other posts.
He said his top priority in coming weeks was to lead a successful referendum campaign to secure voter support for the European Union's next treaty. Ireland is the only EU member holding a popular vote on the Treaty of Lisbon.