Alan Graham MacDiarmid ONZ (April 14, 1927–February 7, 2007) was a chemist, and one of three recipients of the Nobel Prize for Chemistry in 2000.

In 1943, MacDiarmid passed the University of New Zealand's University Entrance Exam and its Medical Preliminary Exam. After completing an MSc in chemistry from the same university, he later worked as an assistant in its chemistry department. It was here that he had his first publication in 1949, in the scientific journal Nature.
He graduated in 1951 with first class honours, and won a Fulbright Fellowship to the University of Wisconsin–Madison.
He majored in inorganic chemistry, receiving his M.S. degree in 1952 and his PhD in 1953. He then won a Shell Graduate Scholarship, which enabled him to go to Sidney Sussex College, Cambridge, where he completed a second PhD in 1955.
He took a faculty position in chemistry at the University of Pennsylvania, where he became a full Professor in 1964.
In 2002, MacDiarmid also joined the faculty of the University of Texas at Dallas.
In 2004, he received the Friendship Award, the highest honor of the People's Republic of China for foreign experts.
The Alan G. MacDiarmid NanoTech Institute at the University of Texas at Dallas was named after him posthumously in 2007.