Pope Honorius I was posthumously excommunicated at the Third Council of Constantinople, with his support for monothelitism deemed to be heretical.

Pope Honorius I was the bishop of Rome from his consecration on 27 October 625 until his death. He actively supported the Christianisation of the Anglo-Saxons, notably by sending Saint Birinus to convert the West Saxons and bestowing the pallium on the archbishops of York and Canterbury, and worked to persuade the Irish and British churches to adopt the Roman Easter computus. He is most noted for his correspondence concerning Patriarch Sergius I of Constantinople, in which he engaged with the Monoenergism controversy and the associated Monothelite doctrines. Honorius was posthumously anathematized by the Third Council of Constantinople (681) for following the Monothelites and confirming their doctrines. This condemnation was confirmed by Pope Leo II, who charged him with failing to extinguish the heresy. The anathema against Honorius I became a primary argument cited by opponents of the definition of papal infallibility during the First Vatican Council (1870).