German astronomer who located the planet Neptune 1846, close to the position predicted by French mathematician Urbain Leverrier.

Galle was born in Saxony, Prussia, and educated at Berlin. He worked at the Berlin Observatory until 1851, when he became professor of astronomy and director of the Breslau Observatory (now in Wroclaw, Poland).
In 1846, Galle received from Leverrier, director of the Paris Observatory, the latter's calculation of the position of a new planet, predicted mathematically from its apparent gravitational effect on Uranus, then the outermost known planet. Within one hour of beginning their search, Galle and his colleague Heinrich d'Arrest (1822-1875) had located Neptune, less than 1° away from the predicted position.
Galle was also the first to distinguish the Crêpe Ring, an inner ring around Saturn, in 1838. He also suggested a method of measuring the scale of the Solar System by observing the parallax of asteroids, first applying his method to the asteroid Flora in 1873. The method was employed with great success after Galle's death.