The Great Comet of 1819, officially designated as C/1819 N1, also known as Comet Tralles, was an exceptionally bright and easily visible comet, approaching an apparent magnitude of 12, discovered July 1, 1819 by the German astronomer Johann Georg Tralles in Berlin. It was the first comet analyzed using polarimetry, by French mathematician Franois Arago.

Johann Georg Tralles (15 October 1763 – 19 November 1822) was a German mathematician and physicist.

He was born in Hamburg, Germany and was educated at the University of Göttingen beginning in 1783. He became a professor at the University of Bern in 1785. In 1810, he became a professor of mathematics at the University of Berlin.

In 1798 he served as the Swiss representative to the French metric convocation, and was a member of its committee on weights and measures. An iron "committee" meter, a duplicate of the prototype archive meter, was then given as a gift to Ferdinand Rudolph Hassler. From 1803 until 1805 these two men worked together on a topological survey of the Canton of Bern.

In 1819, he discovered the Great Comet of 1819, Comet Tralles, named after him.He was the inventor of the alcoholometer, a device for measuring the amount of alcohol in a liquid.

He died in London, England. The crater Tralles on the Moon is named after him, as is the alcoholometer he invented.