From the truncated premiership of Romano Prodi in 2008 to the curtailed mandates of Silvio Berlusconi, Mario Monti and Enrico Letta, 89-year-old Napolitano has presided over a particularly turbulent period in Italy.
He agreed to serve an unprecedented second term in 2013 in order to bring much-needed stability to Italy amid a fierce political deadlock, but said at the time that he would resign before the second seven-year mandate was up.
His nine years in office saw the country's gravest economic recession since the post-war period and the challenges of a rapidly changing society that has become increasingly pessimistic. Austerity-hit Italians, however, have consistently given Napolitano a far higher approval rating in opinion polls than party politicians.
He has campaigned on issues that politicians have failed to tackle, including prison overcrowding and the lack of opportunity for young people. Napolitano has also called in increasingly strong terms for a reform of the electoral law, widely blamed for deadlock which ushered him back into power.
His re-election made him the first Italian president to receive a second mandate. The veteran held the rare quality of being respected by both right and left and an ability to stay above the party political fray.
While the post of president in Italy is largely ceremonial, it takes on vital importance during times of political crisis when the president can help steer the formation of a new government.
Only the president can call early elections - although this is not possible in the last six months of the mandate, a rule that had hampered his attempts to resolve the 2013 crisis.
Born in Naples on June 29th 1925 into a family of intellectuals, Napolitano forged his political career during the Second World War when he took part in the resistance against Nazi and fascist troops, founding a communist group in 1942.
At the end of the war, in 1945, he became an official member of the Italian Communist Party, entered politics and was elected to parliament for the first time in 1953 after earning a law degree. He had ambitions to become a theatre actor but instead he rose through the ranks of the party and became a member of its National Committee on economic issues.
Napolitano was one of the most influential leaders of the party's reformist wing, although he notoriously supported the Soviet Union's invasion of Hungary in 1956 to crush a liberal revolution. He made amends on a visit to Budapest in 2006 when he laid a wreath at the grave of Hungarian revolution leader and national hero Imre Nagy.
With the collapse of the USSR, the Italian Communist Party was officially disbanded in 1991. The current Democratic Party is its main heir.
Napolitano was speaker of the lower house from 1992 to 1994, later becoming interior minister in Romano Prodi's first centre-left government between 1996 and 1998. The following year he won a seat in the European Parliament, serving as a left-wing MEP until 2004.
He was elected to the presidency in 2006 - the first former communist to hold the post - on the third day of voting and with only the support of Prodi's centre-left.
Despite his communist past, his candidacy for president was seen as having the tacit support of the Vatican and he developed friendly relations with now Pope Emeritus Benedict XVI.
He is married to Clio, a former left-wing labour lawyer whom he wed in a civil ceremony, and the couple have two children.