Idun Reiten (born 1 January 1942) is a Norwegian professor of mathematics. She is considered to be one of Norway's greatest mathematicians today.^[2] With national and international honors and recognition, she has supervised 11 students and has 28 academic descendants as of March 2024. She is an expert in representation theory, and is known for work in tilting theory and Artin algebras.^[3]

She took her PhD degree at the University of Illinois in 1971, becoming the second Norwegian woman to earn a PhD in mathematics.^[4] She was appointed as a professor at the University of Trondheim in 1982,^[5] now named the Norwegian University of Science and Technology.

Her research area is representation theory for Artinian algebras, commutative algebra, and homological algebra. Her work with Maurice Auslander now forms the part of the study of Artinian algebras known as Auslander–Reiten theory.

In 2005, Reiten received the Humboldt Research Award.^[6] In 2007, Reiten was awarded the Möbius prize. In 2009 she was awarded Fridtjof Nansen's award for successful researchers, (in the field of mathematics and the natural sciences), and the Nansen Medal for Outstanding Research.^[7]

In 2007, she was elected a foreign member of the Royal Swedish Academy of Sciences. She is also a member of the Norwegian Academy of Science and Letters, the Royal Norwegian Society of Sciences and Letters, and Academia Europaea.^[8]

In 2012, she became a fellow of the American Mathematical Society.^[9] She was named MSRI Clay Senior Scholar and Simons Professor for 2012-13.^[10]

She delivered the Emmy Noether Lecture at the International Congress of Mathematicians (ICM) in 2010 in Hyderabad^[11] and was an Invited Speaker at the ICM in 1998 in Berlin.^[12]

In 2014, the Norwegian King appointed Reiten as commander of the Order of St. Olav "for her work as a mathematician".^[13]

She is the namesake of the IDUN: From PhD to Professor program at the Norwegian University of Science and Technology Faculty of Information Technology and Electrical Engineering, which aimed at "increasing the number of female scientists in top positions at NTNU's Faculty of Computer Science and Electrical Engineering."^[14]

• Krull–Schmidt category