The suspects 37 of them former military personnel face possible life sentences on charges that include attempted assassination, overthrow of the constitutional order and other crimes against the state.
The defendants are accused of attacking the hotel in the resort of Marmaris where Erdogan was staying, killing two policemen. Erdogan had left the hotel shortly before it was stormed.
Turkey has blamed the coup on the movement led by US-based cleric Fethullah Gulen, whose followers are accused of infiltrating the military and other state institutions. Gulen denies orchestrating the failed coup.