Sultan Haji Ahmad Shah Al-Musta’in Billah ibni Almarhum Sultan Abu Bakar Ri’ayatuddin Al-Mu’azzam Shah was Sultan of Pahang from 1974 until his abdication in 2019, and previously the seventh Yang di-Pertuan Agong, the constitutional monarch of Malaysia from 1979 to 1984. His abdication as Sultan was decided by the Royal Council at an extraordinary meeting on 11 January 2019. A special amendment was passed on the state constitution that gave the body more power for this decision, citing the Sultan's incapability to rule due to his failing health. The abdication announced the next day which was retroactively effective on the day of the Royal Council meeting, paving the way to his son, Abdullah to succeed him as Sultan immediately, and subsequently be elected as the next Yang di-Pertuan Agong later the same month.

Sultan of Pahang is the title of the hereditary constitutional head of Pahang, Malaysia. The current sultan is Al-Sultan Abdullah ibni Sultan Ahmad Shah. He is the Head of Islam in the state and the source of all titles, honours and dignities in the state. Historically, the title was also used by rulers of the Old Pahang Sultanate.