The name "Katwijk" probably has its origins in the name of a Germanic tribe called the Chatten (Chatti). The Dutch word "wijk" means "area", so the name probably meant something like "the Chatti area".
In Roman times, Katwijk was a place of strategic importance. It was located at the Roman Empire's northern border, at the mouth of the Rhine river, which in Roman times was larger in this area than it is today. There was a good deal of traffic along the Rhine. Katwijk was also a jumping-off point for the voyage to Britain. Built during the reign of Emperor Claudius (41-54), the town's name was Lugdunum. The town's name was later associated with the name of the city of Leiden, but this is now thought to be incorrect.
After the Romans left the settlement was abandoned and the area largely depopulated, except for small, isolated groups of Frisians ekeing out a living along the changing coast. The area was Christianized by British and Irish missionaries around the 9th century.
Starting around the 12th century the population began to grow. In 1231, the first reference to Catwijck appeared in the records. At this time Katwijk aan Zee was little more than a few wooden houses.
A reference to a fish market on the beach appeared in the records around 150 years later. In 1388, the fish market was moved from Katwijk aan den Rijn to Katwijk aan Zee. Katwijk aan Zee and Katwijk aan den Rijn were part of the same heerlijkheid called "Beide de Katwijken en 't Zand" (or something similar). They have been administratively joined for centuries.
In 1520 a Roman ruin known as Brittenburg emerged from the shifting sands on the beach just south of the mouth of the Oude Rijn, much to everyone's astonishment. It became the subject of a number of prints and paintings. It was square in shape, each side measuring 75 m, and the ruins stood about 3 m high. Eventually it disappeared back under the shifting sands. Attempts have been made to find it again, but to
