529 Morsi supporters facing death
The court in Minya issued its ruling after only two sessions in which the defendants' lawyers complained that they had no chance to present their case.
Those convicted are part of a group of 545 defendants on trial for the killing of a police officer, the attempted killing of two others, attacking a police station and other acts of violence.
More than 150 suspects stood trial; the others were tried in absentia. Sixteen were acquitted.
The defendants were arrested after violent demonstrations which were a backlash for the police crackdown in August on pro-Morsi sit-ins in Cairo in which hundreds of people were killed.
The verdicts - and the extremely harsh sentences - are likely to be overturned on appeal, rights lawyers said.
"This is way over the top and unacceptable," said Mohammed Zarie, who heads a rights centre in Cairo. "It turns the judiciary in Egypt from a tool for achieving justice to an instrument for taking revenge."
"This verdict could be a precedent both in the history of Egyptian courts and perhaps, tribunals elsewhere in the world," he added.
The mass nature of the trial testifies to the determination of Egypt's military-backed government to break the Muslim Brotherhood group and leave no room for political reconciliation with the country's largest Islamist bloc, from which Morsi hails.
The rioting was a backlash for the August 14 police crackdown on two pro-Morsi sit-in camps in Cairo, which killed hundreds of people and sparked days of unrest across the country.
Egypt's military toppled Morsi in July, after four days of massive demonstrations by his opponents demanding that he step down for abusing power during his year in office.
Since the ousting and the August dispersal of the Cairo sit-ins, his Brotherhood and other Islamist supporters have staged near-daily demonstrations that usually descend into violent street confrontations with security forces.
The military-backed government in the meantime unleashed a wave of arrests, detaining hundreds, including top Brotherhood leaders.
At the same time, militant bombings, suicide attacks and other assaults - mostly by an al Qaida-inspired group - have increasingly targeted police and military forces in retaliation for the crackdown on Islamists.
The authorities have blamed the Brotherhood for the violence, branding it a terrorist organisation and confiscating its assets. The group has denied any links to the attacks and has denounced the violence.
Today, another mass trial against Morsi's supporters is opening, also in Minya, with 683 suspects facing similar charges. The defendants in that case include Brotherhood leader Mohammed Badie, who also faces multiple other trials, and senior members of the group from Minya.