Some of the handcuffed defendants were jeered as they were individually escorted into court by police and armed guards in front of TV cameras.
The trial focuses on events at the Akinci airbase which it is alleged was the plotters’ headquarters.
It is taking place in a purpose-built courtroom outside the capital Ankara.
The defendants face charges from attempting to assassinate the president to murder. As some arrived at court they were met by protesters chanting “We want the death penalty!”