Dionysius Adrianus Petrus Norbertus "Dion" Koolen was a Dutch Roman Catholic politician who served as a member of the House of Representatives from 1905 until 1925, as minister of Labour, Commerce and Industry between 1925 and 1926, and as a member of the Council of State from 1926 until his death in 1945. He was a member of the General League of Roman Catholic Electoral Associations and its successor, the Roman Catholic State Party (RKSP).