Saeculum obscurum is a name given to a period in the history of the Papacy during the first half of the tenth 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. The period was first identified and named by the Italian Cardinal and ecclesiastical historian Caesar Baronius in his Annales Ecclesiastici. Other scholars have dated the period more broadly or narrowly, and other terms such as Pornokratie ('pornocracy') and Hürenregiment ('rule of the harlots') have been coined by Protestant German theologians since the Nineteenth Century. Historian Will Durant refers to the period from 867 - 1049 as the "nadir of the papacy".^[1] Baronius' primary source for his history of this period was Liudprand of Cremona whose objectivity is by no means assured.

During this period, the Popes were influenced strongly by a powerful aristocratic family, the Theophylacti, and their relatives.^{[citation needed]} They were in particular under the influence of powerful women (though not prostitutes), especially Theodora and her daughter Marozia. It is widely believed^{[by whom?]} that Marozia was the concubine of Pope Sergius III and the mother of Pope John XI. She was also accused of arranging the murder of Pope John X (who had originally been nominated for office by Theodora) in order to secure the elevation of her current favourite as Pope Leo VI.^{[citation needed]}

Theodora and Marozia undoubtedly held great sway over the popes during this time.^{[citation needed]} In particular, as political rulers of Rome they had effective control over the election of new popes. However, it is debatable whether all of the allegations that have been made against them can be substantiated. Much that is alleged about the saeculum obscurum comes from the histories of Liutprand, bishop of Cremona. Liutprand took part in the Assembly of Bishops which deposed Pope John XII and was a political enemy of Rome. He is described by the Catholic Encyclopedia as "ever a strong partisan and frequently unfair towards his adversaries". Some of what church historians consider the worst excesses of the time might thus be considered to be no more than ecclesiastic gossip or slander.

• Pope Sergius III (904–911), alleged lover of Marozia
• Pope Anastasius III (911–913)
• Pope Lando (913–914)
• Pope John X (914–928), allegedly killed by Marozia
• Pope Leo VI (928–928)
• Pope Stephen VII (928–931)
• Pope John XI (931–935), son of Marozia, alleged son of Pope Sergius III
• Pope Leo VII (936–939)
• Pope Stephen VIII (939–942)
• Pope Marinus II (942–946)
• Pope Agapetus II (946–955)
• Pope John XII (955–963), grandson of Marozia, by her son Alberic II of Spoleto.

• List of sexually active popes
• Pope Joan (legendary, probably fictional; legends about her may have stemmed from stories about the Pornocracy)
• Papal appointment

• Church and Society in a Crisis Age: Tenth and Eleventh Century Europe by Harlie Kay Gallatin.
• The Catholic Encyclopedia entry on Liutprand of Cremona