Sheikh Saad, who was 78, had been ill for several years since he was diagnosed with cancer in 1997.
He was admired by the local population, especially for his role as a figurehead for the resistance during the Iraqi invasion of Kuwait in 1990-91.
For many years, Sheikh Saad combined the roles of crown prince and prime minister. Ill health forced him to relinquish the position of prime minister in 2003, but he remained crown prince until the death of emir Sheikh Jaber al-Sabah in early 2006.
After Sheikh Jaber’s passing, Sheikh Saad automatically become emir in accordance with the constitution. However, his frail condition meant that he could not read the oath of office and after just nine days in the role, the state’s National Assembly (parliament) voted current Emir, Sheikh Sabah al-Ahmed al-Sabah, in as head of state.
Ironically, a letter of abdication from Sheikh Saad arrived just minutes after the vote, but too late to prevent him from becoming the first royal ruler in the region to be democratically ousted from office. Since then, Sheikh Saad was affectionately known as Father Emir by Kuwaitis.
Campaigning for parliamentary elections on 17 May was suspended following his death, although they will still go ahead as planned.