Margaret I may refer to:
- Margaret I, Countess of Flanders (died 1194)
- Margaret I of Scotland (1283 – 1290), usually known as the Maid of Norway
- Margaret I, Countess of Holland (1311 – 1356), Countess of Hainaut and Countess of Holland
- Margaret I, Countess of Burgundy (1310 – 1382), daughter of Philip V, Countess Palatine of Burgundy, Countess of Artois, countess-consort of Flanders, Nevers & Rethel
- Margaret I of Denmark (1353 – 1412), Queen of Denmark, Norway and Sweden (also later Regent of Sweden), and founder of the Kalmar Union