Lee Hee-ho, who had been battling liver cancer, died at 11.37 p.m. (local time) in Seoul on Monday. She is considered one of the pioneers of women's rights in South Korea.
Lee, who was born in 1922, had served as Chair of the Kim Dae Jung Peace Centre, which was founded by the former President to promote inter-Korean reconciliation and fight global poverty, Efe news reported.
Lee accompanied her husband Kim who served as President for five years from 1998 to Pyongyang in 2000 for the first inter-Korean summit with then top leader of North Korea Kim Jong Il, father of the current leader Kim Jong-un.
After the former South Korean President's death in 2009, Lee attended a funeral of Kim Jong Il , where she met Kim Jong-un.
Lee again visited North Korea in August 2015 at the invitation of Kim Jong-un, touring children's hospitals and daycare centres in Pyongyang.
South Korean President Moon Jae-in posted a message from Finland, saying he regrets that he could not take Lee to Pyongyang when he visited there in 2018. He said he believes Lee will support him from heaven to achieve peace.
Inter-Korean relations are at a standstill after the second summit between the North and the US ended without agreement in February.
( With inputs from IANS )