Since the beginning of the year North Korea has embarked on an unprecedented path of meetings with both the South and the US.
Yet talks with Washington have reached deadlock, with both sides so far agreeing only to very general goals.
South Korea has taken on a key mediating role.
South Korean President Moon Jae-in and his wife Kim Jung-sook arrived in Pyongyang on Tuesday morning for the three-day visit.
They were warmly welcomed from the plane by Mr Kim and his wife, Ri Sol-ju.
It's the first trip to the North Korean capital by a leader from the South in a decade.
It is Mr Moon's third meeting with the North's Kim Jong-un since their historic summit at the border in April this year.
The Korean War ended in 1953 with an armistice - but no formal peace treaty was signed.