Jacobus (Jac) van Looy was a Dutch painter and writer.

Van Looy was the son of a carpenter, but his father lost his job when his eyesight began to fail. His mother died when he was five years old and when his father died soon afterwards, he ended up in the Haarlem municipal orphanage. He trained to become a house painter, but was able to follow drawing classes, from 1877 at the "Rijksacademie van Beeldende Kunsten" in Amsterdam.

In 1884, he received the Prix de Rome, which allowed him to travel. The years 1885-86 he spent traveling through Italy, Spain, and Morocco. He was a pupil of August Allebé, Jan Jacob Goteling Vinnis, Dirk Jan Hendrik Joosten, and Hendrik Jacobus Scholten. There he began to draw sketches, which are collected in two volumes. Until 1894 he lived in Amsterdam, when he married Titia van Gelder and moved to Soest. In 1901, he spent another year in Spain and Morocco. He moved back to Haarlem in 1913, when the orphanage where he grew up was converted to the Frans Hals Museum. He bought a house on the corner of the Haarlemmerhout park, where he was often seen taking walks and served as an inspiration for Godfried Bomans, among others. After his death this house was converted to a museum in his name (now only visible with a plaque on the facade).