Prosecutors argued that Yoon ordered the operation to provoke Pyongyang and create a pretext for martial law.
Yoon Suk Yeol's life sentence for insurrection "offers a rare example of democratic resilience", experts say.
Yoon Suk Yeol's December 2024 martial law bid fundamentally damaged South Korea's democracy, a judge told the court.
Yoon still faces two trials over his botched martial law order, and multiple charges.
His short-lived martial law declaration in December 2024 threw the country into months of turmoil.
A court is due to deliver its verdict in the insurrection trial of Yoon Suk Yeol.
Kim Keon Hee was also ordered to return a Graff diamond necklace and pay back 12.85m won in cash.
This is the first of the verdicts in the four trials linked to Yoon's shock decree in 2024.
