Under the constitution, Shaikh Saad, 75, automatically replaces the amir Shaikh Jaber al-Ahmad al-Sabah at the helm of the Arab Gulf state where he has been crown prince since 1978.
He also served as prime minister from February 1978 until July 2003, but was then replaced by Shaikh Sabah al-Ahmad al-Sabah after his health condition deteriorated.
Shaikh Sabah, who is widely expected to be named crown prince, has been Kuwait's strongman running day-to-day affairs due to the poor health of both the late amir and the crown prince.
Shaikh Saad is from the al-Salem branch of the ruling al-Sabah family, which by tradition alternates the position of head of state in the oil-rich nation with the al-Jaber branch, represented by the late amir.
The new amir prides himself on saving the regime during the 1990 Iraqi invasion, and is seen by his people as the hero of liberation. He was given credit for convincing the amir to leave Kuwait for Saudi Arabia.
His return to Kuwait in March 1991, one week after the country was liberated from Iraqi occupation by a multinational force led by the United States, was another high point in his career.
He was the first high-ranking member of the ruling family to return home, and as he left the plane he knelt in prayer as a huge crowd cheered.
The new amir’s profile
The prince, a corpulent man, was nonetheless a target of criticism from the merchant class and liberal MPs who accused him of slowing down economic reform in the oil-rich emirate.
Shaikh Sabah al-Ahmad al-Sabah is
tipped to be the next crown prince
Cutbacks in government subsidies and welfare provision are seen by liberals as a necessary evil in the country's attempt to balance its budget and attract foreign investment into the oil-dependent economy.
Shaikh Saad opposed a large reduction in welfare spending and its generous cradle-to-grave provisions for Kuwaiti nationals, who pay no taxes.
Born in 1930, Shaikh Saad is the eldest son of the late Shaikh Abdullah al-Salem al-Sabah, the 11th amir of Kuwait, known as the father of independence and the constitution.
Shaikh Saad received his basic education in Kuwait before joining Handen Police College in England, where he attended specialised courses in police and security affairs until 1954.
He held various posts in the Kuwaiti police and public security services until 1959, when he was appointed deputy director of the Police and Public Security Department. He remained in that post until 1961.
The new crown prince
In January 1962, Shaikh Saad was appointed interior minister in the first Kuwaiti cabinet after independence from Britain the previous year. In 1964, he was also put in charge of defence.
Kuwait parliament must approve
the next crown prince
In early 1997, he underwent colon surgery and his health has deteriorated since then. He has travelled regularly to Britain and the United States for tests and treatment.
Due to poor health, he delegated extensive authority to Shaikh Sabah for several years until 2003 when the posts of crown prince and prime minister were separated for the first time.
Married to his immediate cousin Shaikha Latifa, he has one son, Fahd, and three daughters. Two other daughters have died.
The crown prince, or heir apparent, must be chosen by the amir within one year of his accession, and the nomination must be approved by the National Assembly, or parliament.
In case the amir's first choice is rejected by parliament, he must nominate at least three of the descendants of Shaikh Mubarak, the founder of Kuwait, and parliament must pledge allegiance to one as heir apparent.