Marian Mięsowicz (born 21.11.1907) is a Polish physicist and a member of the Polish Academy of Sciences (1964), and its vice-president in 1969 — 77. He was born in Lvov. He graduated from the University of Kraków, where he works (professor from 1948). In 1961—77 he was also director of the Institute of Nuclear Technology of the Academy of Mining and Metallurgy, and from 1970 head of the high-energy physics department of the Institute of Nuclear Physics (Kraków).
His research is in the field of applied nuclear physics, cosmic-ray physics and high-energy physics. He put forward (independently of K. Niu) the concept of fireballs, according to which, in the interaction of high-energy hadrons with nuclei, the generation of new hadrons proceeds through a stage in which so-called fireballs are formed (called clusters in accelerator practice). He carried out a large body of research on the interactions of hadrons of ultra-high energies.
The State Prizes of the Polish People's Republic (1952, 1964, 1979). He founded a school of physicists in Kraków.