Mohamed Badie, top leader of Egypt's outlawed Muslim Brotherhood, was sentenced to life in jail along with 14 others on Monday on charges of murder and inciting violence during clashes near Cairo last year.
The session had been summoned for witness statements but the judge surprised journalists and others present by issuing a verdict. Badie, 71, is among hundreds of Brotherhood members already sentenced to death in mass trials that have drawn criticism from Western governments and human rights groups.
The death sentences are subject to appeal.
In what is known as the Bahr al-Azam case, Badie and the other defendants were convicted of the murder of five people and the attempted murder of 100 others during violence that broke out in Giza on July 15, 2013.
Then-army chief Abdel Fattah el-Sissi toppled president Mohamed Morsi of the Muslim Brotherhood on July 3, 2013 after protests against his rule.
Egyptian authorities have since arrested thousands of Brotherhood supporters, sentencing hundreds to death or long prison sentences, while Egypt's oldest Islamist movement has been banned and designated a terrorist organization.
Sissi, who went on to win a presidential election, vowed in his campaign that the Brotherhood, once among Egypt's most formidable political movements, would cease to exist under him.
Morsi, freely elected in 2012, is also on trial on a variety of charges including inciting violence and conspiring with a foreign power, and could face the death penalty if convicted.
Egypt's Brotherhood renounced violence as a means of political change decades ago and argues that it has been robbed of political power won fairly at the ballot box.
Badie and 182 Muslim brotherhood supporters were sentenced to death in a mass trial last June over violence that erupted in Minya governorate which led to the killing of a police officer.
A court sentenced Badie to life in prison in a separate case in July for inciting violence and blocking a major road north of Cairo during protests that followed Morsi's ouster. He received another life sentence last month, on separate counts of inciting violence in clashes near a mosque in Giza.