Ecevit, a political force in Turkey for nearly half a century, died in a military hospital in Ankara after nearly six months in a coma following a stroke. He was 81.
He served as Turkey's prime minister five times, winning his first election in 1973 while leader of the left-of-centre Republican People's Party (CHP), which was founded by Mustafa Kemal Ataturk, the creator of modern Turkey.
His government collapsed in 1974 and his second administration, which took office in 1977, lasted only a month.
He was back in charge in 1978, but resigned after just 21 months.
He was interned for months after a 1980 military coup and banned from politics for years.
But he re-emerged at the head of the Democratic Left Party (DSP), which had been set up by his wife, Rahsan, in 1985.
In January 1999, he led a minority government with the sole task of taking Turkey into elections in April. His party emerged as the biggest in those elections and he forged a coalition with the centre-right Motherland Party and the far-right Nationalist Action Party.
But the tide turned when financial turmoil struck in November 2000 and February 2001, dragging the country into a severe economic crisis.
"Our sorrow is deep. We have lost a great statesman and a leader. His light however, will continue to shine over this country forever"
Zeki Sezer, the chairman of the DSP
In 2002 his party suffered a crushing defeat at the hands of Recep Tayyip Erdogan's, the Turkish prime minister, newly formed Justice and Development party (AKP).
Ecevit won just 1 per cent of the vote, the worst electoral defeat of his political career, as voters blamed him for the millions of layoffs that followed the economic crisis.
Born in Istanbul in 1925, Ecevit was educated at London and Harvard universities.
Before his political career he was known as a writer and poet, translating T.S. Eliot and Ezra Pound into Turkish.
He worked as a journalist in the 1950s with a newspaper close to the CHP.
He entered parliament in 1957 and took over the leadership of the CHP in 1972.
Fiesty to the end, he told the English-language New Anatolian newspaper earlier this year that Turkey's current ruling AKP, which has Islamist roots, posed a threat to the country's secular order.
He said: "I believe our regime is under serious threat."
He said that Erdogan's government bore some responsibility for the shooting of a judge in an Ankara courtroom by a man reportedly protesting over Turkey's ban on the Islamic headscarf in public offices.
"It is the end of an era. He has put a stamp on Turkish political life"
Murat Yetkin, a columnist for Radikal newspaper
He said: "The government openly encouraged those terrorists [by supporting an easing of the headscarf ban]...The unfortunate attack is proof that Turkey will face a very serious situation unless the government changes its mentality."
A group of about 30 of his supporters gathered outside the hospital on Sunday, news reports said.
Ahmet Necdet Sezer, the Turkish president, issued a statement praising Ecevit.
He said: "The Turkish people will always respectfully remember his services to the country."
Murat Yetkin, a columnist for Radikal newspaper, said: "It is the end of an era. He has put a stamp on Turkish political life."
Zeki Sezer, who replaced Ecevit as the chairman of the DSP, said outside the hospital: "Our sorrow is deep. We have lost a great statesman and a leader. His light however, will continue to shine over this country forever."