Katwijk ( pronunciation ) is a coastal municipality and town in the province of South Holland, which is situated in the mid-western part of the Netherlands.

The Oude Rijn ("Old Rhine") river flows through the town and into the North Sea.

Katwijk is located on the North Sea, northwest of Leiden and 16 km north of The Hague. It shares its borders with the municipalities of Noordwijk, Teylingen, Oegstgeest, Leiden, and Wassenaar.