An Egyptian court issued the sentence to the bearded 64-year-old and more than 100 co-defendants over jail breaks during the 2011 uprising that ousted his predecessor, Hosni Mubarak.
Morsi, sitting in a caged dock and wearing the blue uniform of convicts, raised his fists in defiance when the judge pronounced the verdict.
Nicknamed "The Spare Tyre" after he emerged as the Muslim Brotherhood's compromise candidate to run in Egypt's first democratic presidential election, Morsi nonetheless had a long history of activism with the Islamist movement.
Taking office in June 2012 after the overthrow of longtime ruler Mubarak, Morsi was president for a year that was marked by deep divisions in Egyptian society, unrest and a crippling economic crisis.
Since being ousted by then-army chief and now President Abdel Fattah al-Sisi in July 2013, the Islamist leader has been languishing in detention as he faces a series of trials.
In the first verdict against him in April, a Cairo court convicted Morsi of inciting violence against protesters during clashes in December 2012 when he was president, but acquitted him of charges of incitement to murder for which he could have faced the death penalty.
He was sentenced to 20 years in jail in that case.
- A Brotherhood figurehead -
Morsi, the son of a farmer, was not the Brotherhood's initial choice for president.
Hailing from the Brotherhood's political wing -- the Freedom and Justice Party -- he was put forward after one of the movement's powerful financiers, Khairat al-Shater, was disqualified on technical grounds.
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On Saturday, Shater was sentenced to death in another trial.
Morsi won the presidential election in 2012 by a narrow margin, with many choosing him in a protest vote against his rival Mubarak's last prime minister Ahmed Shafiq.
But Morsi quickly grew to be disliked by millions, accused of failing to represent all Egyptians and trampling the ideals of the anti-Mubarak uprising.
The veteran Islamist with a cropped beard and spectacles was hardly charismatic and was seen by many as lacking the will to truly lead.
"He was a puppet of the Muslim Brotherhood," said Cairo University political professor Mustapha Kamel al-Sayyid.
"He appointed Brotherhood members in key administrative posts and that really irritated the bureaucracy and the people."
Since being ousted amid mass protests, Morsi has steadfastly rejected the authority of Egypt's courts to try him.
Often seen in a soundproof glass cage in the dock, Morsi has accused military chiefs of violating the constitution and carrying out a coup.
Morsi was born in the village of El-Adwah in the Nile Delta province of Sharqiya in 1951, and had been the spokesman of the Brotherhood from 2010.
He graduated with an engineering degree from Cairo University in 1975 and received a doctorate from the University of Southern California, where he was also an assistant professor in the early 1980s.
Married with five children and three grandchildren, Morsi first entered the political arena in 2000 when he was elected to parliament as an independent, given the Mubarak-era ban on the Brotherhood.