Teodor Ionescu (born 8.02.1899) is a Romanian physicist and a member of the Academy of Sciences of the Socialist Republic of Romania (1955). He was born in Dorohoi. In 1923 he received the degree of doctor at the University of Iași, and in 1924 at the University of Nancy as well. In 1925—41 he was professor of experimental physics at the University of Iași and in 1941—69 at the University of Bucharest.
His research was in the field of electron and ion physics, nuclear physics and plasma physics.