Theodor Franz Eduard Kaluza (November 9, 1885 – January 19, 1954 ) was born in Ratibor Germany, which is now Raciborz in Poland. He was mathematician and physicist known for the Kaluza-Klein theory involving field equations in five-dimensional space.

Kaluza entered the University of Königsberg to study mathematics and gained his doctorate with a thesis on Tschirnhaus transformations. Kaluza was primarily a mathematician but began studying Relativity. In April 1919 Kaluza noiced that when he solved Einstein's equations for General Relativity using five dimensions, Maxwell's equations for electromagnetism emerged spontaneously. Kaluza wrote to Albert Einstein who encouraged him to publish. His theory was published in 1921 in a paper, "Zum Unitätsproblem der Physik" with Einstein's support in Sitzungsberichte Preussische Akademie der Wissenschaften 96, 69. (1921)

Kaluza's insight is remembered as the Kaluza-Klein theory (also named after another mathematician Oskar Klein) However the work was neglected for many years as attention was directed towards quantum mechanics. His idea that fundamental forces can be explained by additional dimensions did not re-emerge until string theory was developed.

For the rest of his career he continued to produce ideas about relativity and about models of the atomic nucleus. Despite Einstein's support Kaluza remained at a low rank (Privatdozent) at Königsberg until 1929 when he was appointed as professor in Kiel. In 1935 he became a full professor at Göttingen where he remained until his death in 1954. Perhaps his finest mathematical work is the textbook 'Höhere Mathematik für die Pracktiker' which was written jointly with G Joos.