Klaas Schilder (19 December 1890 – 23 March 1952) was a Dutch Neo-Calvinist theologian and professor in the Reformed Churches in the Netherlands (Dutch Gereformeerde Kerken in Nederland or GKN) and later in the Reformed Churches in the Netherlands (liberated) (Dutch Gereformeerde Kerken (vrijgemaakt)). Schilder resisted the German invasion and opposed the Nazi conquest. He was arrested by the Germans in August 1940 and later released. Because he was so outspoken, Schilder spent much of the war in hiding. Schilder was married to Johanna Walter. They had four children.