Kronborg (Danish pronunciation: [ˈkʰʁoːnˌpɒˀ]) is a castle and historical stronghold in the town of Helsingør, Denmark. Immortalised as Elsinore in William Shakespeare's play Hamlet, Kronborg is one of the most important Renaissance castles in Northern Europe. It was inscribed on the UNESCO World Heritage List in 2000.

The castle is situated on the extreme northeastern tip of the island of Zealand at the narrowest point of the Øresund, the sound between present Denmark and the provinces of present Sweden. The latter were under Danish control at the time the castle was built. In this part, the sound is only 4 kilometres (2.5 mi) wide, hence the strategic importance of maintaining a coastal fortification at this location commanding one of the few outlets of the Baltic Sea.

The castle's story dates back to a stronghold, Krogen, built by King Eric VII in the 1420s. Along with the fortress Kärnan in Helsingborg, on the opposite coast of Øresund, it controlled the entrance to the Baltic Sea. From 1574 to 1585, King Frederick II had the medieval fortress radically transformed into a magnificent Renaissance castle. The main architects were the Flemings Hans Hendrik van Paesschen and Anthonis van Obbergen. The sculptural work was coordinated by Gert van Groningen.

In 1629, a fire destroyed much of the castle, but King Christian IV subsequently had it rebuilt. The castle has a church within its walls. In 1658, Kronborg was besieged and captured by the Swedes, who took many of its valuable art treasures as war booty.

In 1785 the castle ceased to be a royal residence and was converted into barracks for the Army. The Army left the castle in 1923. After a thorough renovation, the complex was opened to the public.

The castle's history dates to a fortress, Krogen (lit. 'the Hook'), built in the early 15th century by the Danish king, Eric of Pomerania. The king insisted on payment of sound dues by all ships wishing to enter or leave the Baltic Sea through the Øresund; to help enforce his demands, he built a powerful fortress at the narrowest point in the Sound. At the time, the Kingdom of Denmark extended across both sides of the Sound. On the eastern shore the Helsingborg Castle had been operating since the Middle Ages. With the two castles and guard ship, Denmark could control all navigation through the Sound.

The castle was built on Ørekrog, a sandy tongue of land stretching into the sea from the coast of Zealand toward the coast of Scania. The castle consisted of a square curtain wall with a number of stone buildings inside. The stone building in the northeastern corner contained the king's residence. The building in the southwestern corner contained a large arched banquet hall. The building in the southeastern corner possibly served as the chapel. Large portions of the walls of Krogen are contained within the present-day Kronborg Castle.

King Christian III had the corners of the curtain wall supplemented with bastions in 1558–1559.