Jonkheer Jan Six (born 25 June 1978), also known as Jan Six XI, is a Dutch art dealer and art historian. Six is a member of the Six family, a descendant of Jan Six, the subject of Rembrandt's Portrait of Jan Six. He is the son of Jan Six X, the present Baron van Hillegom. In 2018, Six identified Portrait of a Young Gentleman, attributed by Christie's as "circle of Rembrandt", as the work of Rembrandt himself. This was the first 'new' Rembrandt identified in 44 years.