| Mathew Brady | United States | 1822–1896 | 12 |
| Mather Brown | United States | 1761–1831 | 12 |
| Mateo Gilarte | Crown of Aragon | 1629–1675 | 9 |
| Mateo Cerezo | Spain | 1637–1666 | 12 |
| Master of the Wendelin Altar | — | — | 1 |
| Master of the Washington Coronation | — | 1300–1400 | 1 |
| Master of the Tversk school | — | — | 2 |
| Master of the Tiburtine Sibyl | Netherlands | 1475–1495 | 2 |
| Master of the Thenn Portraits | — | 1450–1600 | 1 |
| Master of the Stroganov school | — | — | 4 |
| Master of the Stockholm Pietà | — | — | 1 |
| Master of the Starck Triptych | — | — | 3 |
| Master of the Sigena chapter house | — | — | 4 |
| Master of the San Lucchese Altarpiece | — | — | 2 |
| Master of the Presentation of Christ | Austria | — | 1 |
| Master of the Passion of Christ | — | 1500–1500 | 1 |
| Master of the Panzano Triptych | — | — | 1 |
| Master of the Palazzo Venezia Madonna | — | — | 4 |
| Master of the Orléans Triptych | — | — | 1 |
| Master of the Oberaltaich Man of Sorrows | — | — | 1 |
| Master of the Novgorod School | — | — | 6 |
| Master of the Murano Gradual | — | 1425–1475 | 1 |
| Master of the Munich Mary Altar | Germany | 1401–1499 | 1 |
| Master of the Monogram TK | — | — | 2 |
| Master of the Monogram IDM | — | 1564–1635 | 2 |
| Master of the Miller Tondo | — | 1478–1530 | 2 |
| Master of the Medici Banquet Decanters | — | 1670 | 2 |
| Master of the Luna Altarpiece | — | — | 4 |
| Master of the Legend Scenes | Germany | 1500 | 22 |
| Master of the Lanckoronski Annunciation | — | — | 1 |
| Master of the Krumlov Madonna | — | 1400–1500 | 1 |
| Master of the High Altar of Saint Jacob's in Nuremberg | — | — | 1 |
| Master of the Habsburgs | — | 1450–1550 | 2 |
| Master of the Greek school | — | — | 2 |
| Master of the Friedrich Altar of 1447 | — | — | 1 |
| Master of the Franciscan Crucifixes | — | — | 2 |
| Master of the Dinteville Allegory | — | — | 1 |
| Master of the Die | — | 1512–1570 | 11 |
| Master of the Death of Saint Nicholas of Munster | Germany | 1490 | 1 |
| Master of the Day of Judgement | — | — | 12 |
| Master of the Cypresses | Spain | — | 8 |
| Master of the Codex Rossiano | Italy | — | 1 |
| Master of the Clarisse Panel | — | 1300 | 1 |
| Master of the Cini Madonna | — | — | 3 |
| Master of the Burg Weiler Altarpiece | Germany | — | 1 |
| Master of the Brussels Calling of Saint Matthew | Habsburg Netherlands | — | 2 |
| Master of the Bracciolini Chapel | — | 1370–1420 | 1 |
| Master of the Borghese Tondo | — | 1450–1520 | 2 |
| Master of the Benediktbeuren Madonna | — | 1380–1450 | 1 |
| Master of the Benediktbeuren Crucifixion | — | 1440–1460 | 1 |
| Master of Staffolo | — | — | 1 |
| Master of Sorpe | — | — | 1 |
| Master of Sopetrán | — | 1450 | 4 |
| Master of Santa Coloma de Queralt | — | — | 1 |
| Master of Sant Esteve d'Andorra | — | — | 4 |
| Master of San Pietro in Sylvis | Italy | — | 1 |
| Master of San Lucchese | — | — | 1 |
| Master of Saint Clare | — | 1250 | 1 |
| Master of Roncaiette | Italy | — | 1 |
| Master of Riglos | Spain | 1450 | 3 |