Saeculum obscurum is a name given to a period in the
history of the Papacy during the first half of the 10th century, beginning with the installation of
Pope Sergius III in 904 and lasting for sixty years until the death of
Pope John XII in 964. During this period, the
Popes were influenced strongly by a powerful and corrupt aristocratic family, the
Theophylacti, and their relatives.