Riazuddin, also spelled as Riaz-Ud-Din (Urdu: رياض الدين; 10 November 1930 – 9 September 2013), was a Pakistani theoretical physicist, specialising in high-energy physics and nuclear physics. Starting his scientific research in physics in 1958, Riazuddin was considered one of the early pioneers of Pakistan's nuclear weapons development and atomic deterrence development. He was the director of the Theoretical Physics Group (TPG) of the Pakistan Atomic Energy Commission (PAEC) from 1974 until 1984. Riazuddin was a pupil of the winner of the 1979 Nobel Prize in Physics, Abdus Salam. Riazuddin carried out his research at the International Centre for Theoretical Physics (ICTP), PAEC, the European Organization for Nuclear Research (CERN) and Daresbury Laboratory where he published papers in mathematics and physics. Riazuddin also played an important role in education in Pakistan, contributing to the rise of science in Pakistan. Riazuddin authored several scientific books on particle physics and quantum mechanics. Later in his life, he joined the National University of Sciences and Technology (NUST) as a visiting professor of theoretical physics. Riazuddin was born in a native Punjabi family in Ludhiana in British Punjab of the British Indian Empire in 1930. After the Partition of India, his family migrated to Pakistan in 1947 and settled in Lahore, West-Pakistan. He is the twin brother of physicist Fayyazuddin. At age 17, Riazuddin attended Punjab University, and took his BSc(Hons) in Mathematics under the supervision of Abdus Salam in 1951. Riazuddin also studied under the supervision of Abdus Salam at the Postgraduate level at Cambridge University. As a student of mathematics, he learned the advanced course on quantum mechanics under Abdus Salam, as he had made the course of quantum mechanics outside the regular curriculum. In 1951, Salam funded his scholarship, and helped him gain admission to the graduate school of Punjab University. In 1953, Salam supervised his MSc in applied mathematics where his master's dissertation dealt with fundamental concepts of mathematical physics.