0802 GMT April 22, 2018
The defendants, who include senior military officers, were each given four life sentences at the trial in the southwestern city of Mugla, state-run media said, AFP wrote.
They include former brigadier general Gokhan Sahin Sonmezates who was accused of directing the plot. Former elite commando Zekeriya Kuzu, who was famously found hiding in a cave four days after the failed coup, also received a life term.
Another key figure in the trial, Erdogan's former military aide-de-camp Ali Yazici, was sentenced to 18 years in jail. Just one suspect, former lieutenant colonel Huseyin Yilmaz, was acquitted.
The trial began on February 20 and is one of many such processes taking place across Turkey to try those who allegedly took part in the failed bid to oust Erdogan on July 15, 2016.
Some verdicts have already been handed out in lower-profile cases but it is the first ruling involving alleged top plotters.
The failed coup left 249 people dead, not including the putschists, and the authorities have vowed no compromise in bringing those involved to justice.
Over 50,000 people have been arrested under the state of emergency imposed following the coup bid.
Turkey accuses Pennsylvania-based cleric Fethullah Gulen of orchestrating the attempted coup. Gulen, a former Erdogan ally turned arch-foe, strongly denies Ankara's claims.
Some of the suspects, including Sonmezates, admitted taking part in the coup bid during the trial but denied any links to Gulen.
Gulen was also on trial in absentia in Mugla. But the judge ruled to separate his case from the trial along with two other suspects.