Salman, 79, had increasingly taken on the duties of the king over the past year as his ailing predecessor and half-brother, Abdullah, became more incapacitated. Abdullah died before dawn on Friday at 90 years old.
Salman had served as defence minister since 2011 and so was head of the military as Saudi Arabia joined the United States and other Arab countries in carrying out airstrikes in Syria in 2014 against the Islamic State, the Sunni militant group that the kingdom began to see as a threat to its own stability.
He takes the helm at a time when the ultraconservative Muslim kingdom and oil powerhouse is trying to navigate social pressures from a burgeoning youth population - over half the population of 20 million is under 25 - seeking jobs and increasingly testing boundaries of speech on the Internet, where criticism of the royal family is rife.
Salman's ascension hands throne to yet another aging son of Saudi Arabia's founder, King Abdul-Aziz Al Saud, who is thought to have had more than 50 sons from multiple wives.
Salman's health has been a question of concern. He suffered at least one stroke that has left him with limited movement on his left arm.
The Saudi throne has for decades passed between Al Saud's sons. Prince Muqrin, the youngest of the sons at 69, was named crown prince in the royal court statement that announced Salman as king.
Each succession has brought the kingdom closer to a time when the next generation - Al Saud's grandsons - will have to take over. Although the family has successfully managed to close ranks throughout the years, a generational change would raise the specter of a power struggle by placing the throne in the hands of one branch at the expense of the others.
King Abdullah had carried out a slow but determined series of reforms aimed at modernising the country, including increasing education and nudging open the margins of rights for women. Salman appears to back those reforms, but he has also voiced concerns about moving too fast.

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