John Seymour Lucas RA (21 December 1849 – 8 May 1923) was a Victorian English historical and portrait painter, as well as an accomplished theatrical costume designer.

Lucas' artistic education included extensive travels around Europe, particularly Holland and Spain, where he studied the Flemish and Spanish masters.

Inspired by van Dyck and particularly Diego Velázquez, he excelled in depicting scenes from the British 16th- to 18th-century Tudor and Stuart periods, including in particular the Spanish Armada, the English Civil War, and the Jacobite rebellions.

It was praised not only for the obvious tension between the muscular blacksmiths and the red-coated forces of law and order (or repression), but for the extraordinary realism in the depiction of the rough smithy and glowing horseshoe on the anvil.

In addition to executing more than 100 major oil paintings and a host of drawings, Lucas was renowned as a set and costume designer for the historical dramas popular on the late Victorian and early Edwardian stages.

However, the end of Pax Britannica and the rise of Modernism left these twin pillars of the Lucas oeuvre slightly marooned and he is less than a household name in the 21st century.