Although the identity of the sitter is unknown his elegant dress and bearing suggest that he was an individual of wealth and distinction. The inclusion of a hunting dog was quite common in portraits of aristocrats, and the gold chains are a usual sign of honor. The suggestion of a military identification is enhanced by the gesture of his hand fisted at his waist, and the standing, three-quarter-length pose was generally used by Mor in his paintings of aristocrats as opposed to the more informal poses he used in his likenesses of middle-class subjects.
The most likely precedent for this painting is the Portrait of Charles V (Prado, Madrid), done in 1532 or 1533 by the Venetian artist Titian. From Titian, Mor adapted the compositional arrangement for his depiction of a standing man with a dog. Similarly, the way that light is employed, brilliantly illuminating selective portions of the figure while arbitrarily obscuring other parts in dark shadow, is thoroughly Titianesque. Mor's style also reveals his training in his native Flanders, in his close attention to detail and delight in depicting textures.
The deft handling of paint and the astute psychological presentation clearly demonstrate why Mor was such a sought-after portraitist during the sixteenth century, anticipating the achievements of the great portraitist of the aristocracy in the following century, Anthony van Dyck.
More information on this painting can be found in the Gallery publication Early Netherlandish Painting, which is available as a free PDF https://www.nga.gov/content/dam/ngaweb/research/publications/pdfs/early-netherlandish-painting.pdf
upper left: Antonius mor pingebat a. 1569
Probably Sir Peter Lely [d. 1680], London. (sale, London, 18 August 1682). George John Spencer, 2d earl Spencer [1758-1834], Althorp House, Northamptonshire, by 1822; The Earls Spencer, Althorp House; Albert Edward John Spencer, 7th earl Spencer [1892-1975], Althorp House, until 1927; (Duveen Brothers, Inc., London and New York); purchased February 1930 by Andrew W. Mellon, Pittsburgh and Washington, D.C.; deeded 28 December 1934 to The A.W. Mellon Educational and Charitable Trust, Pittsburgh; gift 1937 to NGA.
- Art Treasures of the United Kingdom: Paintings by Ancient Masters, Art Treasures Palace, Manchester, 1857, no. 513, as His Own Portrait by Sir Antonio More.
- Special Exhibition of National Portraits Ending with the Reign of King James the Second, South Kensington Museum, London, 1866, no. 186.
- Exhibition of the Royal House of Tudor, Corporation of Manchester Art Gallery, Manchester, 1897, no. 126.
- Dutch Exhibition, Whitechapel Art Gallery, London, 1904, no. 140.
- Exhibition of Works by the Old Masters, Royal Academy of Arts, London, 1907, no. 8.
- Flemish and Belgian Art, 1300-1900, Royal Academy of Arts, London, 1927, no. 231.
The painting has been transferred from a panel to a canvas support. The original support was composed of three boards joined vertically. The background, originally very thinly painted, is now somewhat abraded and has been rather heavily inpainted, perhaps to give it a more finished appearance. In addition, a strip about one inch wide has been repainted along the margin of the painting on all sides. Inpainting is also evident in two vertical strips along the former join lines, in the beard of the sitter to the left of his mouth where there is a rather large loss, and in small scattered patches on his forehead, cheeks, and hands. The signature and date appear to be original, though the signature has been reinforced.
 Presumably the painting was transferred after Duveen acquired it, when it was also cleaned and restored. In the catalogue of the 1927 Royal Academy exhibition, no. 231, and in earlier catalogues it is described as on panel.
- Dibdin, Thomas Frognall. Aedes Althorpianae; or, An Account of the Mansion, Books, and Pictures, at Althorp, The Residence of George John, Earl Spencer, K.G. ... 2 vols. London, 1822: 1:262-263, repro. opp. 262.
- Catalogue of the Pictures at Althorp, the Seat of Right Honorable the Earl Spencer, K. G.. Northampton, 1823: 23.
- Walpole, Horace, George Vertue, and James Dallaway. Anecdotes of Painting in England: with some account of the principal artists; and incidental notes on other arts; collected by the late George Vertue; digested and published from his original MSS. 5 vols. London, 1826-1828: 1:240.
- Passavant, Johann David. Tour of a German Artist in England. Translated by Elizabeth Eastlake. 2 vols. London, 1836: 2:35.
- Catalogue of the Pictures at Althorp House in the County of Northampton, with occasional Notes, Biographic and Historical. London, 1851: no. 271.
- Waagen, Gustav Friedrich. Treasures of Art in Great Britain: Being an Account of the Chief Collections of Paintings, Drawings, Sculptures, Illuminated Mss.. 3 vols. Translated by Elizabeth Rigby Eastlake. London, 1854: 3:457.
- Kramm, Christian. De levens en werken der Hollandsche en Vlaamsche kunstchilders, beeldhouwers, graveurs, en bouwmeesters. 6 parts and supplement in 3 vols. Amsterdam, 1857-1864: 4:1160-1161.
- Bürger, W. [Théophile Thoré] Trésors d'art en Angleterre. Brussels and Ostende, 1860: 173-174.
- Blanc, Charles. École Hollandaise. 2 vols. Histoire des peintres de toutes les écoles 1-2. Paris, 1861: 1:4, 8, repro. 1 (engraving of head).
- Pierre-Marcel, René. "Collection du Comte Spencer." Les arts 60 (December 1906): 8, repro. 5.
- Friedländer, Max J. "Die Winterausstellung der Royal Academy in London 1907." Repertorium für Kunstwissenschaft 30 (1907): 378.
- Loga, Valerian von. "Antonis Mor als Hofmaler Karls V. und Philipps II." Jahrbuch der kunsthistorischen Sammlungen in Wien 27 (1907/1909): 112, fig. 22.
- Scheewe, Ludwig. "Antonis Mor." In Thieme-Becker. 37 vols. Leipzig, 1907-1950: 25(1931):111.
- Hymans, Henri. Antonio Moro son oeuvre et son temps. Brussels, 1910: 114-115.
- Friedländer, Max J. Die altniederländische Malerei 14 vols. 1924-1937. Leiden, 1936: 13:172, no. 354. (English ed., 14 vols., 1967-1976. Leiden, 1975: 13:102, 118, no. 354, pl. 176.)
- Tipping, H. Avray. English Homes. 9 vols. London, 1926: 9:repro. 315.
- Benkard, Ernst. Das Selbstbildnis vom 15. bis zum Beginn des 18. Jahrhunderts. Berlin, 1927: xxviii-xxix, 24-25, pl. 31.
- Marlier, Georges. "Antonis Mor van Dashorst (Antonio Moro)." Académie Royale de Belgique. Classe des Beaux-Arts Mémoires. Series 2.3. Fasc. 2 (1934): 22, 79-83, 96-97, no. 11, fig. 11.
- Cortissoz, Royal. An Introduction to the Mellon Collection. Boston, 1937: 35-36.
- De Tolnay, Charles. "Flemish Paintings in the National Gallery of Art." Magazine of Art 34 (1941): 189-191, 200, figs. 20-22.
- Duveen Brothers. Duveen Pictures in Public Collections of America. New York, 1941: no. 190, repro., as Self-Portrait (Presumed).
- Preliminary Catalogue of Paintings and Sculpture. National Gallery of Art, Washington, 1941: 135, no. 52.
- Book of Illustrations. National Gallery of Art, Washington, 1942: 240, repro. 28.
- Frerichs, L. C. J. Antonio Moro. Amsterdam, 1947: 39, 57, repro. 52.
- Friedländer, Max J. "Frans Pourbus der Ältere." Oude Holland 57 (1947): 65-66, fig. 6.
- Paintings and Sculpture from the Mellon Collection. National Gallery of Art, Washington, 1949 (reprinted 1953 and 1958): 66, repro.
- De Vries, A. B. "Antonio Moro." Les arts plastiques. Series 6.3 (1953): 206, fig. 95.
- Broadley Hugh T. Flemish Painting in the National Gallery of Art (Booklet no. 5 in Ten Schools of Painting in the National Gallery of Art, Washington, DC). Washington, 1960: 9, 34-35, color repro.
- Wilenski, R. H. Flemish Painters 1430-1830. New York, 1960: 168, 608, pl. 428.
- Müller Hofstede, Justus. "Zur frühen Bildnismalerei von Peter Paul Rubens." Pantheon 20 (1962): 286-287, fig. 13.
- Puyvelde, Leo van. La peinture flamande au siècle de Bosch et Breughel. Paris, 1962: 264, fig. 142.
- Walker, John. National Gallery of Art, Washington, D.C. New York, 1963 (reprinted 1964 in French, German, and Spanish): 306, repro.
- Philippot, Paul. "Le portrait à Anvers dans la seconde moitié du XVIe siècle." Bulletin des Musées Royaux des Beaux-Arts de Belgique 14 (1965): 173, fig. 4.
- Summary Catalogue of European Paintings and Sculpture. National Gallery of Art, Washington, 1965: 93.
- European Paintings and Sculpture, Illustrations. National Gallery of Art, Washington, 1968: 82, repro.
- Ragghianti, Carlo L. "Pertinenze francesi nel cinquecento." Critica d'Arte 19, n.s. 122 (1972): 46, 73, fig. 53.
- European Paintings: An Illustrated Summary Catalogue. National Gallery of Art, Washington, 1975: 244, repro. 245.
- De Meyere, J. A. L. "Utrechtse schilderkunst in de tweede helft van de 16de eeuw." Jaarboek Oud-Utrecht (1978): 145, fig. 26.
- Groeneveld, Elizabeth E. H. "Een herziene biographie van Anthonis Mor." Jaarboek van het Koninklijk Museum voor Schone Kunsten Antwerpen (1981): 115.
- Walker, John. National Gallery of Art, Washington. Rev. ed. New York, 1984: 259, no. 325, color repro.
- European Paintings: An Illustrated Catalogue. National Gallery of Art, Washington, 1985: 283, repro.
- Hand, John Oliver and Martha Wolff. Early Netherlandish Painting. The Collections of the National Gallery of Art Systematic Catalogue. Washington, 1986: 202-205, color repro. 203.
- National Gallery of Art. National Gallery of Art, Washington. New York, 1992: 48, repro.
- Hand, John Oliver. National Gallery of Art: Master Paintings from the Collection. Washington and New York, 2004: 125, no. 96, color repro.
- Pergam, Elizabeth A. The Manchester Art Treasures Exhibition of 1857: Entrepreneurs, Connoisseurs and the Public. Farnham and Burlington, 2011: 313.