Johann Bayer (1572 – March 7, 1625) was a German astronomer and lawyer. He was born in Rain, Bavaria in 1572. He began his study of philosophy in Ingolstadt in 1592, and moved later to Augsburg to begin work as a lawyer. He grew interested in astronomy during his time in Augsburg. He ultimately became legal advisor to the Augsburg city council in 1612 and died in 1625.

He is most famous for his star atlas Uranometria, published in 1603, which was the first atlas to cover the entire celestial sphere. It introduced a new system of star designation which has become known as the Bayer designation as well as some of the modern constellations.

The Bayer crater on the Moon is named after him.