Marie, Baroness Vetsera (March 19, 1871–January 30, 1889) was Crown Prince Rudolf of Austria's mistress, the daughter of Baron Alban Vetsera, a diplomat in foreign service at the Austrian court, and his wife Helene Baltazzi. The two lovers were found dead under mysterious circumstances at Emperor Franz Joseph's hunting lodge, (the incident is known as Mayerling, after the name of the lodge.)

It has been variously claimed that she was killed by Crown Prince Rudolf, who then killed himself; that they both killed themselves; that they killed one another; that the two of them were murdered; and that she either was or was not pregnant at the time of her death.

Her body was spirited out of Mayerling and interred in the Cistercian monastery at Heiligenkreuz . Helmut Flatzelsteiner exhumed her body (without permission); she was reinterred in her original grave in October 1993.