Andrzej Mostowski (born 1 november 1913 in Lwów, Poland - 22 august 1975 in Vancouver, Canada) was a Polish mathematician.

Mostowski entered University of Warsaw in 1931. He was influenced by Kuratowski, Lindenbaum and Tarski. His Ph.D. came in 1939, officially directed by Kuratowski but in practice directed by Tarski who was a young lecturer at that time.

He became an accountant after the Nazi invasion of Poland but continued working in the Underground Warsaw University . After the Warsaw uprising of 1944 the Nazis tried to put him in a concentration camp. With the help of some Polish nurses he escaped to a hospital, choosing to take bread with him rather than his notebook containing his research. Some of the research he reconstructed after the War but much was lost.

This work was largely on recursion theory and undecidability. From 1946 until his death he worked at the University of Warsaw. Much of work during that time was on first order logic and model theory.