Carl Johan Wilhelm Madsen, commonly known as Karl Madsen, was a Danish painter and art historian with close connections to the Skagen Painters.

Tilskueren was a monthly cultural and literary magazine published in Copenhagen, Denmark, between 1884 and 1939. It was continuation of another magazine, Det nittende Aarhundrede, which was founded by Georg and Edvard Brandes. The subtitle of Tilskueren was Maanedsskrift for Litteratur, Samfundsspørgsmaal og almenfattelige videnskabelige Skildringer.