Alexander Mikhailovich Prokhorov (born Alexander Michael Prochoroff, Russian: Алекса́ндр Миха́йлович Про́хоров; 11 July 1916 – 8 January 2002) was an Australian-born Soviet-Russian physicist and researcher whose work focused on quantum electronics. His most famous and well-known works were on optics and electromagnetic research. He was jointly awarded the Nobel Prize in Physics in 1964 with Charles Hard Townes and Nikolay Basov for his fundamental work that led to the development of the laser and the maser.

Alexander Michael Prochoroff was born on 11 July 1916 at Russell Road, Peeramon, Queensland, Australia (now 322 Gadaloff Road, Butchers Creek, situated about 30 km from Atherton), to Mikhail Ivanovich Prokhorov and Maria Ivanovna (née Mikhailova), Russian revolutionaries who had emigrated from Russia to escape repression by the Tsarist regime. As a child he attended Butchers Creek State School.

The family returned to Russia in 1923, after the culmination of the October Revolution and the Russian Civil War.

In 1934, Prokhorov entered the Saint Petersburg State University to study physics. He was a member of the Komsomol from 1930 to 1944, the youth wing of the CPSU. Prokhorov graduated with honors in 1939 and moved to Moscow to work at the Lebedev Physical Institute, in the oscillations laboratory headed by academician N. D. Papaleksi. His research there was devoted to propagation of radio waves in the ionosphere.

At the onset of World War II, in June 1941, he joined the Red Army. Prokhorov fought in the infantry, was wounded twice in battles, and was awarded three medals, including the Medal For Courage in 1946. He was demobilized in 1944, a year before the end of WWII and eventual victory of the Allies.

Prokhorov returned to the Lebedev Institute where, in 1946, he defended his Ph.D. thesis on "Theory of Stabilization of Frequency of a Tube Oscillator in the Theory of a Small Parameter".

In 1947, Prokhorov started working on coherent radiation emitted by electrons orbiting in a cyclic particle accelerator called a synchrotron. He demonstrated that the emission is mostly concentrated in the microwave spectral range. His results became the basis of his habilitation on "Coherent Radiation of Electrons in the Synchrotron Accelerator", defended in 1951. By 1950, Prokhorov was assistant chief of the oscillation laboratory. Around that time, he formed a group of young scientists to work on radiospectroscopy of molecular rotations and vibrations, and later on quantum electronics. The group focused on a special class of molecules which have three (non-degenerate) moments of inertia. The research was conducted both on experiment and theory. In 1954, Prokhorov became head of the laboratory. Together with Nikolay Basov he developed theoretical grounds for creation of a molecular oscillator and constructed such a device based on ammonia. They also proposed a method for the production of population inversion using inhomogeneous electric and magnetic fields. Their results were first presented at a national conference in 1952, but not published until 1954–1955.

In 1955, Prokhorov started his research in the field of electron paramagnetic resonance (EPR). He focused on relaxation times of ions of the iron group elements in a lattice of aluminium oxide, but also investigated other, "non-optical", topics, such as magnetic phase transitions in DPPH. In 1957, while studying ruby, a chromium-doped variation of aluminium oxide, he came upon the idea of using this material as an active medium of a laser. As a new type of laser resonator, he proposed, in 1958, an "open type" cavity design, which is widely used today. In 1963, together with A. S. Selivanenko, he suggested a laser using two-quantum transitions. For his pioneering work on lasers and masers, in 1964, he received the Nobel Prize in Physics shared with Nikolay Basov and Charles Hard Townes.