Prince Salman has been appointed the new crown prince of Saudi Arabia, becoming the next-in-line to 88-year-old King Abdullah's throne.
The appointment, by royal decree quoted on state television, comes after Crown Prince Nayef bin Abdul Aziz al-Saud died in Geneva on Saturday.
Prince Salman, 76, is the current defence minister and has been governor of the capital Riyadh for many decades.
Prince Nayef, who was 78, died during medical treatment.
Prince Salman bin Abdul Aziz al-Saud is thought to be pragmatic and more liberal-minded than his late brother, who was seen as more conservative than King Abdullah and personally committed to maintaining strict religious traditions.
However, the move had been widely expected and is unlikely to bring any substantial change, BBC Arab affairs analyst Sebastian Usher reports.
But the announcement has again postponed the potentially difficult but inevitable transition to a younger generation, our analyst says.
Prince Salman will stay on as defence minister and also becomes deputy prime minister.
He is part of the same influential Sudairi faction as his late brother and the late King Fahd.
The group is formed of the sons of the late King Abdul Aziz by a favourite wife, Princess Hassa al-Sudairi.
Prince Salman's younger brother Prince Ahmed becomes interior minister, state television said, while King Abdullah remains prime minister.
Prince Ahmed had served as deputy to Prince Nayef at the interior ministry for many years.