IJmuiden is a port town located in the Dutch province of North Holland. It serves as the main settlement within the municipality of Velsen, which lies primarily to the south-east. The town straddles the mouth of the North Sea Canal that connects to Amsterdam, featuring large sea locks at this critical junction. To the south, it borders the Zuid-Kennemerland National Park, a reserve of plant-covered dunes, while the north bank hosts a steel plant and the district of Velsen-Noord.

The area was originally known as Breesaap before plans for a canal to Amsterdam were initiated in the 19th century. IJmuiden was founded on 1 November 1876 when King William III officially opened the North Sea Canal, dubbing the town after passing through the locks. The name literally means mouth of the IJ. It is considered the newest city in North Holland, established to shortcut Amsterdam's harbours' passage to the sea for incoming vessels.

The town is defined by its industrial and maritime infrastructure, including the world's largest North Sea locks capable of closing a lane fifty metres wide. It contains four harbors: a fishing dock, haringhaven, IJmondhaven, and Seaport Marina. The area also features two fortified pens constructed by the German navy during World War II to house fast torpedo boats and midget submarines, which remain significant historical structures today.

Visitor appeal centers on its industrial heritage along the European Route of Industrial Heritage, known as the Holland Route. Key sites include the Hoogovensmuseum, the system of sluice gates, and the Zee- en Havenmuseum. The town hosts the annual North Sea Race yacht race and is home to the headquarters of the Royal Netherlands Sea Rescue Institution. The history of the town during the war is documented in the Bunker Museum IJmuiden.

The statistical area has a population of 30,466, while the broader verified fact cites 48,320 as of 2009. The economy was boosted by the Koninklijke Nederlandse Hoogovens steelworks in 1918 and remains tied to shipping and fishing. DFDS Seaways operates routes via IJmuiden, and the harbour coastline serves as a measuring point for the UK-Netherlands sea boundary. The town is situated ten kilometres north northwest of Haarlem.