June 15 - Pope Leo X issues the bull Exsurge Domine (Arise O Lord), threatening Martin Luther with excommunication if he does not recant his position on indulgences and other Catholic doctrines.
July 1 - La Noche Triste (Night of Sorrow): The forces of Cuitláhuac, Aztec ruler of Tenochtitlan, gain a major victory against the forces of conquistadorHernán Cortés. This results in the death of about 400 conquistadors and some 2,000 of their Native American allies. However, Cortés and the most skilled of his men manage to escape and later regroup.