Maria Catharina van Grunsven (1918–2004), also known as Riet van Grunsven or Riet van de Haterd-van Grunsven, was an armed member of the Dutch Resistance during World War II.
One of 21 people who became “line crossers,” special agents who helped to maintain a secret connection between occupied and liberated Netherlands across the waterways of the Biesbosch and the Merwede, she operated as a courier for part of the larger Biesbosch resistance group, and the Albrecht intelligence group.
During this resistance work, she was given the aliases “Ice Block” and “Trouble.”In recognition of her valor, she was honored with a personal audience with Queen Wilhelmina of the Netherlands in 1946, and was awarded the Bronzen Leeuw (the Bronze Lion), which was personally presented to her by Prince Bernhard of the Netherlands in 1949.