The name Helsingør is derived from the word hals meaning "neck" or "narrow strait", referring to the narrowest point of the
Øresund (Øre Sound) between what is now Helsingør and Helsingborg, Sweden.
The people were mentioned as Helsinger (which may mean "the people of the strait") for the first time in King Valdemar the Victorious's Liber Census Daniæ from 1231 (not to be confused with the Helsings of Hälsingland in Sweden).
Placenames show that the Helsinger may have had their main fort at Helsingborg and a fortified landing place at Helsingør, to control the ferry route across the strait.
Helsingør as it is known today was founded in the 1420s by the Danish king Eric of Pomerania. He established the Sound Dues in 1429, meaning all foreign ships passing through the strait had to pay a toll, which constituted up to two-thirds of Denmark's state income. With this income Eric of Pomerania built the castle Krogen. The castle was expanded in the 1580s and renamed Kronborg. All ships had to stop in Helsingør to get their cargo taxed and pay a toll to the Danish Crown, but it also generated a significant trade for the town. In 1672 Helsingør had grown into the third biggest town in Denmark.
Johan Isaksson Pontanus (Rerum Danicarum Historica, 1631) attributes a long and partially fictitious history to Helsingør.
The Sound Dues were abolished in 1857 with the Copenhagen Convention, where all naval nations agreed to pay a one-time fee.
The oldest known fortified building of Helsingør is Flynderborg, an early medieval fortress situated on a hill just south of the medieval city.
Around 1200, the first church, Saint Olaf's Church, was built.
A number of convents once surrounded the church, but now all that remains is the church building, today the cathedral of the Diocese of Helsingør. The oldest parts of the cathedral of Helsingør date back to the 13th century and tell us that the fishermen's village, as Helsingør was then, had grown to a town of importance.
In World War II, Helsingør was among the most important transport points for the rescue of Denmark's Judaism during the Holocaust. Adolf Hitler had ordered that all Danish Jews were to be arrested and deported to the concentration camps on Rosh HaShanah, the Jewish New Year which fell on October 2, 1943. When
Georg Ferdinand Duckwith, a Danish Nazi party maritime attache received word of the order on September 28, 1943, he shared it with political and Jewish community leaders. Using the name Elsinore Sewing Club (Danish: Helsingør Syklub) as a cover for messages, the Danish population formed an underground railroad of sorts, moving Jews away from the closely watched Copenhagen docks to spots farther away, especially Helsingør, just two miles across the Øresund from Helsingborg in neutral Sweden. Hundreds of civilians hid their fellow Danish citizens -- Jews -- in their houses, farm lofts and churches until they could board them onto Danish fishing boats, personal pleasure boats and ferry boats. In the span of three nights, Danes had smuggled over 7200 Jews and 680 non-Jews (gentile family members of Jews or political activists) across the Øresund, to safety in Helsingborg and Malmö in Sweden.