The date was decided during a closed-door meeting of cardinals at the Vatican on Monday, the first since the funeral of Pope Francis on Saturday.
The Catholic Church's top dignitaries will retire to the Sistine Chapel in strict seclusion, with all contact with the outside world forbidden.
A two-thirds majority of the 134 cardinals expected to be involved in the Conclave is needed to choose Francis' successor in a process that could take days if not weeks.
The 16th-century Sistine Chapel was closed to tourists on Monday to allow for vote preparations.
With AAP.
