Duli Yang Maha Mulia Sultan Sir Ahmad Tajuddin Akhazul Khairi Waddien ibni Almarhum Sir Sultan Mohammad Jamalul Alam II (commonly referred to as Sultan Ahmad Tajuddin), KBE, CMG (22 August 1913 – 3 June 1950) was the 27th sultan of Brunei from 11 September 1924 until his death.
His reign represented the start of a new era in Brunei. The discovery of oil changed the whole course of Brunei's history and enabled faster development in all sectors of the country. The expansion and improvement of formal education and his encouragement of religious education were some of his additional contributions to Brunei Darussalam.
Sultan Ahmad Tajuddin was born on 22 August 1913 at the Palace in Brunei Town. He is the fifth child of 10 children to the late Sultan Sir Muhammad Jamalul Alam II and his wife, Raja Isteri Pengiran Anak Siti Fatimah. His younger brother Pengiran Muda Omar Ali Saifuddien will became his future successor.
He received his early education in the palace. Teachers who had been assigned to teach him is Cikgu Salleh Hj Masri. Salleh Haji Masri was one of the famous freedom fighters with anti-colonial sentiments. His relationship with Salleh is close and good. Not only him, there are also the sons of the chiefs of state also accompanied him learn.