Stephen VIII was born of a Roman family, and prior to becoming pope was attached to the church of Saints Silvester and Martin. With his elevation as Bishop of Rome, Stephen gave his attention to the situation in West Francia, or as the Romans still referred to it, Gaul. In early 940, Stephen intervened on behalf of Louis IV of France, who had been trying to bring to heel his rebellious dukes, Hugh the Great and Herbert II, Count of Vermandois, both of whom had appealed for support from the German king Otto I. The Pope dispatched a Papal legate to the Frankish nobles, instructing them to acknowledge Louis, and to cease their rebellious actions against him, under threat of excommunication. Although the embassy did not achieve its stated objective, it did have the effect of removing the support of the Frankish bishops who had been backing Hugh and Herbert.
Emboldened by this, Stephen then sought to break up the alliance against Louis by offering Herbert's son, Hugh of Vermandois, the office of Archbishop of Reims. Along with the Pallium (the symbol of office for the archbishop), Stephen sent another legate, with instructions to the Frankish nobility, insisting that they submit to Louis. This time they were informed that if the pope had not received their embassies by Christmas, notifying him of their intent to submit to the king, they would be excommunicated. This time, there was a shift in support to Louis, as a number of the more important nobles declared for him, and by the end of 942, all of the nobility had affirmed their loyalty to Louis, and notified the pope of their intent.
Closer to home, things were a lot more difficult for Stephen. The continuing domination of the Counts of Tusculum was evident throughout Stephen's pontificate, as it was during that of his predecessors and successors (see Saeculum obscurum). Although Stephen was subject to Alberic II of Spoleto, Prince of the Romans, and did not in reality rule the Papal States, Stephen himself was not a member of that family, nor had he any relationship with Marozia, who had dominated Roman and papal politics during the preceding decades. Stephen was however caught up in the ongoing conflict between Alberic II and Hugh of Italy, with Hugh besieging Rome in 940. After a failed assassination attempt against Alberic, which involved a number of bishops, Alberic cracked down on any potential dissent in Rome, with his enemies either scourged, beheaded or imprisoned. If there is any truth to Martin of Opava’s account of the torture and maiming of Stephen VIII by supporters of Alberic (see below), it must have occurred at this juncture, in the aftermath of the conspiracy, and just prior to Stephen's death.
On 17 August 942, Alberic summoned a council in Rome, where he demonstrated his control over the papacy by making use of various papal officials, such as the Primicerius, the Secundicerius of the Notaries, and the Vestararius. Stephen died during October 942, and was succeeded by Marinus II.