Pope Francis, 88, died from a stroke that led to a coma and irreversible heart failure, the Vatican said. His death was confirmed using an echocardiogram.
His final testament requests a simple burial at the Basilica of Saint Mary Major in Rome.
Cardinals will convene to plan the funeral, which is expected to be attended by world leaders, including Donald Trump.
Landmarks globally, including the Eiffel Tower and Empire State Building, were dimmed or lit in his memory.
Cardinal Kevin Farrell, the Camerlengo, will oversee Vatican administration during the interim period before a new pope is elected.