John Scolvus or John of Kolno may have been a navigator of the late 15th century. It has been claimed he was among a group of early Europeans to reach the shores of the Americas prior to Columbus, arriving in 1476 as steersman of Didrik Pining, although this view is not supported by contemporary evidence, and as he is not mentioned contemporaneously, his identity and even existence have been disputed.
It has been claimed that in the 1470s, a fleet of several Danish ships sponsored by Christian I of Denmark set sail from Norway westwards to Greenland. There was such a fleet in 1473 or 1476, commanded by John of Kolno, supposed to be a Polish navigator at the service of the king of Denmark. According to speculations lacking surviving written references, the fleet was commanded by two Baltic sailors and pirate hunters, Didrik Pining and Hans Pothorst, possibly also including the Portuguese João Vaz Corte-Real on one of the journeys. It has been claimed that from the Western coast of Greenland they may have reached the North American mainland. The story can not be verified today, since the only surviving records tell us that Pothorst and Pining saw a "rocky island called Hvitsark, halfway between Iceland and Greenland" in 1494, as described by Samuel Eliot Morison in his "The European Discovery of America, The Northern Voyages". John of Kolno ("Jan z Kolna" in Polish, eventually "Jan Scolvo") by contrast, was a navigator who led a Danish fleet to the coast of Labrador in 1476, or even 1473, according to one source, at the command of Christian I of Denmark.
It is not certain if John Scolvus really existed and whether he reached America aboard these ships. All sources mentioning him were written long afterwards. Some evidence could suggest that Scolvus did exist and sailed to some location in the North Atlantic. Primarily, a 1536 globe of cartographer Gemma Frisius depicts an area within the Arctic Circle, north of a strait dividing Terra Corterealis and Baccalearum Regio from the westward projection of Greenland. Within this area is the inscription, "Quij, the people to whom Joes Scoluss, a Dane, penetrated about the year 1476."