Carstian Luyckx, also known as the Monogrammist KL, was a Flemish painter and draughtsman who specialized in still lifes in various subgenres including flower still lifes, fruit still lifes, fish still lifes, pronkstillevens (sumptuous still lifes), vanitas still lifes, hunting pieces and garland paintings. He also painted animals and a few genre scenes. After starting his career in Antwerp he is believed to have worked later in France.

Carstian Luyckx was born in Antwerp in 1623 as the son of David Luycx en Margriet Cloot. He was baptized on 17 August 1623. He studied painting under Philips de Marlier, a still life specialist, in 1642 and under Frans Francken III, a history painter, in 1645.

In 1645 he became a master of the Antwerp Guild of St. Luke. He is documented in Antwerp up to August 1653. It is believed that he left Antwerp and worked in France as many of his later works carry French inscriptions. During his residence in France, Luyckx influenced other vanitas painters, including Simon Renard de St. André.

It is not clear when and where Luyckx died but his death date is assumed to fall between the years 1657 and 1677.