1950
Pope Pius XII, declared infallibly, ex cathedra:
Mary, having completed the course of her earthly life, was assumed body and soul to heavenly glory.

(The Magisterium has stayed conspicuously silent regarding whether this process entailed Mary's physical death. The teaching merely states that Mary's body and soul were assumed at the completion of the course of Mary's life.)
Picture of Pope Pius XII St Peter's Basilica