Most of the 529 were arrested during violent clashes which erupted in the southern province of Minya after two Muslim Brotherhood protest camps in Cairo were forced to break up on 14 August.
The charges against the group include violence, inciting murder, storming a police station and damaging public and private property.
The mass sentencing is a sign of an escalation of the crackdown on the Muslim Brotherhood movement and on supporters of the former president Mohammed Morsi, who was ousted last July in a military coup.
The government has declared the Muslim Brotherhood a “terrorist” group since the coup last summer: the Brotherhood maintains that it is a peaceful movement, and that President Morsi’s removal was unlawful.
Only 123 of the defendants were present at the court in Minya: the rest had either been released, were out on bail or on the run.
“The court has decided to sentence to death 529 defendants and 16 were acquitted,” lawyer Ahmed al-Sharif told Reuters. The ruling is expected to be appealed.
The mass sentencing comes as a group of Al Jazeera journalists return to court, charged with spreading false news and being part of a terrorist organisation – charges that the news organisation denies.