This paper reveals the identity and authorship of an unknown Portrait of a Gentleman previously attributed to the circle of Diego Velázquez. Based on the peculiar physiognomy of the sitter, and in comparison to other known portraits, it can be identified as Don Francisco Fernández de la Cueva, 8th Duke of Alburquerque (1619-1676), Viceroy of New Spain (1653-1660) and Sicily (1668-1670). Albuquerque was known to be in Flanders between 1640 and 1643, during which time he was portrayed by siblings Michaelina and Charles Wautier, to whom the painting can now be attributed for stylistic and historical reasons, and supported by evidence of the remains of a signature in the upper left-hand corner of the canvas. This paper traces the career of the Duke of Albuquerque, which is linked to the history of Spain, Flanders, Mexico, and Sicily, highlighting his inclination towards the Fine Arts, whilst delving into his polemic participation in the Battle of Rocroi in 1643.