Ali al-Naimi, who held the post of oil minister for more than two decades, was one of the most powerful figures within the OPEC oil cartel.
But recently his influence appeared to have been curbed by the growing power of Salman's son Prince Mohammed who has taken charge of economic policy.
Naimi has been replaced by Khaled al-Faleh, previously health minister, who takes the enlarged portfolio of energy, industry and mineral resources, according to a royal decree announced Saturday by state media.