A son of a miller, at eleven years of age, he became a student at Leipzig, Saxony university. Three years later he continued his studies at the Alma Mater Rudolfina in Vienna, Austria. There he became a pupil and friend of Georg von Peurbach. In 1457 he built an astrolabium, in 1465 a portable sundial for pope Paul II. From 1461-65 Johannes Müller or Regiomontanus lived and worked at Cardinal Bessarion's house in Rome. From Rome he went to work at the court of Matthias I, King of Hungary. He calculated and made extensive astronomical tables. He also built astronomical instruments.
In 1471 Johannes Müller moved to the Free City of Nuremberg in Franconia, which at that time was one of the most important places of learning, publication, commerce, artistry etc of the empire. Regiomontanus remains known for building the first Astronomical observatory of Germany, perhaps of Europe, at Nuremberg. He made and printed many astronomical charts.
1475 he went and worked with pope Sixtus IV in Rome on Calendar Reform. While in Rome, Müller died mysteriously; some say of the plague, others (more feasibly) of assassination. It was July 6, 1476, and he had just turned forty exactly one month earlier.
Johannes Müller was internationally famous already during his lifetime. He was a very active writer. Despite his plans for writing four times the volume he acually did get to finish, he left us a number of works.
It is not true that after his death he simply became known for the place of his birth, Königsberg or in Latin: Regiomontanus. In fact, the story is much more interesting: It happens that in the time of Müller it was common for scholars to author their works under Latin pennames. Copernicus did likewise and that is why we do not know him as Zepernik, as he was really called. By the same token, the only reason we know Regiomontanus by this place-name is that we can only know him, as is true for everyone sooner or later, by the very words he wrote.