The first traces of civilization in Konstanz date back to the late Stone Age. Around 50 AD, the first Romans settled on the site. Its name, originally Constantia, comes either from the Roman emperor Constantius Chlorus, who fought the Alemanni in the region and fortified the town around 300 AD, or from his grandson Constantius II, who visited the region in 354.
Trade thrived during the Middle Ages; Konstanz owned the only bridge in the region which crossed the Rhine, making it a strategic place.
In 1414–1418 the Council of Constance took place, during which, on 6 July 1415, Jan Hus (Czech religious thinker, philosopher and reformer), who was seen as a threat to Christianity by the Roman Catholic Church, was burned at the stake. The Konzilgebäude or “Konzil” where the conclave was held can still be found at the harbour.
Konstanz became part of the German Empire in 1871 during the unification of Germany. After World War I it was included within the Republic of Baden. Because it practically lies within Switzerland, directly adjacent to the Swiss border, Konstanz was not bombed by the Allied Forces during World War II. The city left all its lights on at night, and thus fooled the bombers into thinking it was actually Switzerland.
The University of Konstanz was established close to the town in 1966. Konstanz was the birthplace of Count Ferdinand von Zeppelin, constructor of the famous Zeppelin airships.