Prussian astronomer, physicist, and biologist whose law (1766) expressing the distances between the planets and the Sun was confirmed by J.E. Bode in 1772.

Having received a degree from the University of Leipzig (1752), Titius joined the faculty of the University of Wittenberg in 1756. The Titius-Bode law (also called Bode's law) proved to be accurate in accounting for the average distance between planetoids and the Sun and also for the distance between Uranus (discovered in 1781) and the Sun. It did not, however, accurately predict the distances of Neptune and Pluto. Although best known for his law, Titius was also active in physics, concentrating on thermometry, and in biology, classifying plants, animals, and minerals.