Layman with the office of protoserinus.
Chosen pope on 4 December963 at the insistence of Emperor Otto the Great following deposition of PopeJohn XII.
During the next two days he was rushed through holy orders, which turned the local laity against him.
When Otto withdrew his forces from Rome in February 954, the opposition to Leo became open, and he had to flee the city and was deposed by a new synod.
The synod chose John XI, who died suddenly of natural causes.
The Roman citizens chose Benedict V, but Otto and his army returned, laid seige to the city, and forced them to accept Leo.