SEOUL - Ms Lee Hee-ho, the widow of former South Korean President Kim Dae-jung, died on Monday (June 10) at the age of 96, aides said.
According to Yonhap news agency, Ms Lee had been hospitalised at a Seoul hospital while battling liver cancer.
"First lady Lee passed today at 11.37pm," an official at the Kim Dae Jung Peace Centre said.
Ms Lee served as chair of the Kim Dae Jung Peace Centre, which was founded by her husband to promote inter-Korean reconciliation and world peace, and fight global poverty.
The former president, who served from 1998 to 2003, is known for his "sunshine policy" of engagement with North Korea. He died in 2009.
Ms Lee accompanied her husband to Pyongyang in 2000 for the historic first inter-Korean summit with then North Korean leader Kim Jong Il.
Kim Dae-jung won the Nobel Peace Prize later that year.
After her husband's death, Ms Lee made two more trips to North Korea, in 2011 and 2015, to continue to push for inter-Korean reconciliation.
In December 2011, she visited the North to pay her respects upon the death of then-leader Kim Jong Il.
"I hope our visit will contribute to improving inter-Korean ties," she said at the time.
The former first lady's visit was highly symbolic as she became one of the first South Koreans to meet with Mr Kim's successor and son and current leader Kim Jon Un.
In August 2015, Ms Lee visited North Korea again upon the personal invitation of Kim Jong Un.
The two did not meet, but Ms Lee visited various children's hospitals and daycare centers in Pyongyang, where she delivered medicine and children's hats that had been knitted by members of her own humanitarian aid organization.
"As I held the hands of the innocent children, I thought to myself that we must not pass down the pain of (inter-Korean) division to future generations," the former first lady said after returning from the four-day visit.
According to Yonhap, Ms Lee had been hospitalised since March. Her condition sharply worsened last Saturday, but had somewhat stabilised since, according to her aides.
A funeral has been planned for Friday and she will be buried at the Seoul National Cemetery.
President Moon Jae-in expressed his condolences on Twitter and Facebook while on a state visit to Helsinki, Finland.
"Today we are seeing off a great person who dedicated her entire life to women," he wrote. "Beyond being the wife of President Kim Dae-jung and a first lady, she belonged to the first generation of women's rights activists in the Republic of Korea."