Aleksander Ilyich Akhiezer (Russian: Алекса́ндр Ильи́ч Ахие́зер; October 31, 1911 – May 4, 2000) was a Soviet theoretical physicist, known for contributions to numerous branches of theoretical physics, including quantum electrodynamics, nuclear physics, solid state physics, quantum field theory, and the theory of plasma. He was the brother of the mathematician Naum Akhiezer.
Akhiezer was born in Cherykaw in what is now Mahilyow Voblast, Belarus. He studied radio engineering at Kiev Polytechnic Institute in 1929–34. From 1934, he worked at the Ukrainian Institute of Physics and Technology in Kharkiv. With Isaak Pomeranchuk and under the supervision of Lev Landau, he studied light-light scattering and was awarded a Ph.D. in 1936.
When Landau left Kharkiv in 1938, Akhiezer became head of the department of Theoretical Physics. A treatise on wave absorption in modulated quasiparticles gave him a habilitation degree in 1941, since when he was full professor at the same place until his death at the age of 89.
With Cyril Sinelnikov and Anton K. Valter he founded the faculty of physics and technology. With Pomeranchuk he studied neutron scattering and plasma physics at the Kurchatov nuclear physics institute in Moscow (1944–52).