Abū Rayḥān Muḥammad ibn Aḥmad Bīrūnī (Persian: ابوریحان محمد بن احمد بیرونی), often known as Alberuni, Al Beruni or variants, (born 5 September 973 in Kath, Khwarezm (now in Uzbekistan), died 13 December 1048 in Ghazni, today's Afghanistan) was a Persian scholar and polymath of the 11th century.

He was a scientist and physicist, an anthropologist and comparative sociologist, an astronomer and chemist, a critic of alchemy and astrology, an encyclopedist and historian, a geographer and traveler, a geodesist and geologist, a mathematician, a pharmacist and psychologist, an Islamic philosopher and theologian, and an scholar and teacher.

He was the first Muslim scholar to study India and the Brahminical tradition, and has been described as the founder of Indology, the father of geodesy, and "the first anthropologist". He was also one of the earliest leading exponents of the experimental scientific method, and was responsible for introducing the experimental method into mechanics and mineralogy, developed comparative sociology and experimentation in psychology, and the first to conduct elaborate experiments related to astronomical phenomena.

George Sarton, the father of the history of science, described Biruni as "one of the very greatest scientists of Islam, and, all considered, one of the greatest of all times." A. I. Sabra described Biruni as "one of the great scientific minds in all history." The crater Al-Biruni on the Moon is named after him. Tashkent Technical University (formerly Tashkent Polytechnic Institute) is also named after Abu Rayhan al-Biruni and a university founded by Ahmad Shah Massoud in Kapisa is named after him.