Quirinus Johan Harder (13 October 1801, in Rotterdam – 21 October 1880, in Vlissingen[1][2]) was a Dutch architect best known for having designed a large number of lighthouses. He worked as a structural engineer for the Loodswezen, the Dutch organization overseeing all maritime pilots. Harder's lighthouses were made of cast iron, a new material at the time, which allowed for segmented fabrication and construction.[3]