Jachthaven Willemsoord is a modern marina and visitor harbour located within the historic Willemsoord complex in Den Helder, Noord-Holland, situated directly on the Natte Dok — a rectangular wet dock originally constructed between 1812 and 1823 as the operational heart of the former Royal Navy shipyard.

Boats approaching from the Waddenzee can reach the marina via the Zeedoksluis, or alternatively through the Koopvaardersschutsluis and on through the Maritieme Binnenhaven, entering the Natte Dok to starboard.

The marina holds the Blauwe Vlag award and offers facilities including a fuel pontoon for diesel, a waste station for black and grey water, and free Wi-Fi.

The surrounding Willemsoord complex, a protected cultural heritage site, has been extensively restored and now includes museums, restaurants, and other amenities within easy walking distance of the harbour.