For most people, it's a four-day break from Thursday to Sunday.
Now, Chuseok, traditionally, is when Korea celebrates the harvest.
These days, it means tens of millions of people hit the road to visit relatives across the country, so it's an exodus from the capital area.
The Korea Expressway Corporation projects around 5-point-17-million vehicles to be on the highways just today.
The roads are jammed up right now, but will clear up this evening.
The journey by car from Seoul to the southern port city of Busan normally takes 4 or 5 hours, but today it's taking around eight hours.
To the southwestern city of Gwangju, it's expected to take over six hours... and to the eastern city of Gangneung, around four hours.