HDMS Ditmarsken (or Ditmarschen) was a 64-gun ship of the line of the Royal Dano-Norwegian Navy which was launched in 1780.

She was captured by the British during the battle of Copenhagen in 1807 and burnt.

Ditmarsken was constructed at Nyholm Dockyard to a design by Henrik Gerner.

She was laid down on 17 December 1779, launched on 25 November 1780 and the construction was completed on 18 March 1783.

She was captured by the British during the battle of Copenhagen in 1807 and burnt.