Leiden is one of the oldest cities of the Netherlands. In ancient times the Romans had a settlement, called Lugdunum Batavorum, a few miles west of where Leiden is currently located. Unfortunately, that historic site is, as a consequence of the ever-changing boundaries between sea and land, currently located a mile off-shore, in the North Sea.

The city of Leiden, however, is still firmly on land. It was first mentioned in a text originating in 860, under the name of Leython. During the Middle Ages the city slowly but steadily grew, and acquired city rights in 1266. This was mostly due to the presence of the Burcht van Leiden, a shell keep built on a artificial hill. This keep was located at the place where two tributaries of the Rhine (namely the Old Rhine and the New Rhine) meet. Being a strategically important location, this keep was in Medieval times often the site of intensive battles.

Over the centuries the Burcht gradually lost its importance, both because the use of canons became more popular, and because the keep itself became more and more enclosed by the growing city of Leiden. The city itself, however, continued to flourish. During the 1400s Leiden became Europes most important broadcloth industry, which became a grand source of income and wealth for the area.

During the 1500s, the Low Countries had come under the rule of the rule of the Spanish Empire, as a consequence of marriages and conquests. However, from the 1560s onwards, the opposition against the Spanish King and his tax regulations grew ever stronger. The opposition soon grew to an open revolt, led by the young nobleman William of Orange, after the (almost by accident) captured the almost undefended city of Brille on the first of April, 1572. This unexpected victory over the Spanish Empire sparked other protest, and the city of Leiden, amongst others, joined the rebellion. However, Leiden was already important, and the Empire laid siege on the city. This siege lasted almost a year, but on the third of October, 1573, the city was relieved by William of Orange. As a recognition of the sacrifice Leiden had made for the Rebels, William founded the first University of the Netherlands in Leiden.