The king's resignation took effect immediately, the National Palace said in a statement. No reason was given and palace officials did not respond to requests for comment.
Malaysia has nine royal households, who typically take turns to sit on the throne. The selection of the next king can be decided by a vote in the Council of Rulers, made up of all nine royal households.
The palace statement said the king was grateful for the opportunity given to him by the Council of Rulers and thanked the prime minister and government.
"His Highness has worked towards fulfilling his responsibilities entrusted to him as the head of state, serving as a pillar of stability, source of justice, the core of unity ... for the people," the palace statement said.
The resignation comes barely a week after the king resumed his duties after spending two months away on medical leave.
Images purporting to show the king getting married in Russia appeared on social media in December. The palace did not respond to requests for comment on the photos or reports of a marriage.
