Johann Friedrich Julius Schmidt (25 October 1825 in Eutin, Germany – 7 February 1884 in Athens, Greece) was a German astronomer and geophysicist. He was the director of the National Observatory of Athens in Greece from 1858 to 1884. Julius Schmidt was tireless in his work, it was suggested by William Henry Pickering that he perhaps devoted more of his life than any other man to the study of the Moon. During his lifetime, he made some of the most complete lunar maps of the 19th century.

According to his own analysis, he mapped no less than 32,856 craters, with Mädler mapping 7,735 and Lohrmann 7,177. Schmidt also mapped 348 lunar rilles. In six years, he made almost 57,000 micrometer settings to make 3050 height measurements of the terrain.

Schmidt was born in the town of Eutin to his father Carl Friedrich Schmidt, a glazier and his mother Maria Elisabeth Quirling. He went to school at a gymnasium in Hamburg, where he impressed with his sense of form and drawing abilities and demonstrated a strong interest in science. In the autumn of 1839, during an auction in his hometown, he stumbled upon a copy of Schröter's book, Selenotopographische Fragmente. As Schmidt himself put it,

“The sight of numerous illustrations of shadow-casting mountains and craters made such a strong and lasting impression that it determined the main direction of my later life.”

Prior to this, 14-year-old Schmidt had been interested in botany and zoology for a while. He could not make the decision to switch careers until he could see for himself what a sight the Moon would grant when viewed through a telescope. That wish was fulfilled when his father made him a "small, very good" telescope which Schmidt used to look at the Moon. Leaning against a lamppost, he recognized the rays of Tycho and immediately made his first attempt at drawing the crater and ray system. This telescope could only magnify 10x, however, the objective was ground according to "Dollond's principle", meaning it was achromatic.

Reading Schröter's work and drawing the Moon became his main occupation, and it was not long until Schmidt devised a tripod for the telescope, which could go in both up-down and left-right motions. Although the execution was rough, the wooden mount made it much easier for him to continue lunar observations. Now he started drawing entire phases, not considering the libration but paying attention to the shadows. Thus passed by 1840, with Schmidt's habits making him neglect school.

In the spring of 1841, Hellwag, a government councilor who was well experienced in astronomy, noticed his efforts. Hellwag asked Hofrath Voss, the son of the well known Eutin school rector, to entrust Schmidt with a 1200mm focal length Dollond telescope which Schmidt found to be very sharp, approximating the magnification to be 15-20x. He saw the bands of Jupiter, Saturn's rings and a crescent Venus for the first time with it.

In July 1841, the Hamburg Gymnasium made a visit to the Altona Observatory, where Schmidt looked through a larger telescope for the first time and became acquainted with the well-known map of the Moon made by Wilhelm Beer and Johann Heinrich Mädler. Dr. Petersen showed him the craters Gassendi and Bullialdus.