Johannes Müller von Königsberg (June 6, 1436 – July 6, 1476), today best known by the Latin epithet Regiomontanus, is a German mathematician, astronomer, astrologer, translator, instrument maker and Catholic bishop.

He was born in the Franconian village of Unfinden, now part of Königsberg, Bavaria—not in the more famous East-Prussian Königsberg.

He is also known as Johannes der Königsberger (Johannes of Königsberg).

His writings are published under the name of Ioannes de Monte Regio, a Latinized version of his name.

Both names mean "John of King's Mountain".

The name "Regiomontanus" will be first coined by Philipp Melanchthon in 1534, fifty-eight years after Regiomontanus' death.