Voting for new president to begin by end of January
The Italian president Giorgio Napolitano signed his letter of resignation at 10.30 on Wednesday 14 January, weeks after stating his intention to resign due to age-related ailments.
Napolitano's resignation coincides with the conclusion of Italy's six-month presidency of the European Union, which ended on 13 January.
The 89-year-old Napolitano was first elected president in 2006 and reluctantly agreed to a second term in April 2013 to end a parliamentary deadlock. He was the 11th president of Italy and the only president to hold a second term of office.
Under the constitution the president of the senate automatically becomes acting president until a new president is elected. Pietro Grasso, an anti-mafia magistrate, politician and president of the senate since March 2013, will be acting president until a successor is appointed.
The president of Italy is elected by both houses of parliament in joint session plus three respresentatives from each region (apart from Valle d'Aosta which only has one). The voting is in secret and a two thirds majority is needed on the first three ballots and then after that by an absolute majority. The office last for seven years.
Potential candidates to succeed Napolitano include Romano Prodi, the former premier and European Commission president, and former premier Giuliano Amato, both of whom have been presidential candidates in the past.
The Italian constitution states that any citizen aged 50 or older on election day can be elected president.