Saeculum obscurum (Latin, the dark age) 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 in the sixteenth century^[1]. Other scholars have dated the period more broadly or narrowly, and other terms, such as the Pornocracy (Template:Lang-de, from Greek pornokratiā, "prostitute rule") and the Rule of the Harlots (Template:Lang-de), were coined by Protestant German theologians in the nineteenth century. Historian Will Durant refers to the period from 867 to 1049 as the "nadir of the papacy".^[2] Baronius' primary source for his history of this period was Liudprand of Cremona.

During this period, the Popes were influenced strongly by a powerful and corrupt aristocratic family, the Theophylacti, and their relatives^[3] . The family originated from Theophylactus, who held positions of increased importance in the Roman nobility such as Judex, vestararius, gloriosissimus dux, consul and senator, and magister militum^[4]. His wife Theodora and daughters, Theodora and Marozia held a great influence over the papal selection and religious affairs in Rome through conspiracies, affairs and marriages^[5].

Marozia became the concubine of Pope Sergius III when she was 15 and later took other lovers and husbands^[6]. She ensured that her son John was seated as Pope John XI according to Antapodosis sive Res per Europam gestae (958-62), by Liutprand of Cremona (c. 920-72). Liutprand affirms that Marozia arranged the murder of her former lover Pope John X (who had originally been nominated for office by Theodora) through her then husband Guy of Tuscany possibly to secure the elevation of her current favourite as Pope Leo VI ^[7]. There is no record substantiating that Pope John X had definitely died before Leo VI was elected since John X was already imprisoned by Marozia and was out of public view.

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. 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."

• Pope Sergius III (904–911), alleged lover of Marozia
• Pope Anastasius III (911–913)
• Pope Lando (913–914)
• Pope John X (914–928), alleged lover of Theodora, 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