Former South Korean President Kim Dae-jung died at the age of 85 at 1:43 p.m. (0443 GMT) Tuesday, Park Chang-il, chief of Seoul's Severance Hospital said.
The direct cause of his death was reportedly complications from pneumonia, Park said.
Due to his age and health conditions, cardiopulmonary resuscitation (CPR), a method to revive heart activities, was not given to Kim, Park added.
Rep. Park Ji-won, former secretary of Kim, held an official press conference and said Kim's death was attended by his family and former aides, expressing thanks to South Koreans and the hospital staffs.
Park said there is yet to be a concrete plan on his funeral, but it is soon to be decided after having a close discussion with the presidential office.
Former President Kim was moved to the hospital on July 13 as he showed symptoms of pneumonia.
Kim, placed under a respirator three days later, showed signs of improvement, but later was put back on it and went on a surgery on his bronchial tubes in late July.
Beginning late Monday night, Kim's health condition exacerbated, with his heart failing intermittently, the hospital officials said.
Kim, taking office in 1998, served as president for five years, during which he met with the Democratic People's Republic of Korea (DPRK) leader Kim Jong-il for the first time since the armistice of the Korean War.
During his presidency, Kim also won the Nobel Prize for his "lifelong" strife for democracy and efforts to realize reconciliation on the Korean Peninsula.