Willem Coucheron (also recorded as Willum or Wyllem Coucheron) was a Dutch-born Dano-Norwegian quartermaster general. He was sent to Copenhagen to present plans for a new defensive work for Halden, Norway. These plans were approved by the king on 28 July 1660. He began the construction of the fortifications of Fredrikstad Fortress at Halden in 1663. Together with his son Anthony Coucheron, he worked on the fortification which became known as Fredriksten fortress in Halden. The defensive walls, built to the Dutch design of the period, were so effective a deterrent that the town, although placed under siege, was never taken.