Adoptiani, a Christian sect in Spain, founded by Elipandus. archbishop of Toledo, and Felix, bishop of Urgel, near the close of the 8th century. They affirmed that Jesus was really the son of God only in his divine nature, and the son of God by adoption merely in his human nature. So long as they confined their efforts to spreading their views in the Mohammedan territory, no notice was taken of the new sect. But when, through the efforts of Felix, whose diocese belonged to the Frankish empire, adoptianism began to spread in the dominion of Charlemagne, the subject was brought to the notice of that emperor, and the synod of Ratisbon (792) condemned it as a renewal of the Nestorian heresy. Felix recanted, and confirmed his recantation before Pope Adrian in Rome. But after his return to Urgel he reaffirmed his adoptian views. At the request of Charlemagne Aleuin wrote an epistle to Felix against adoptianism. This step, however, had no results; on the contrary, a number of the Spanish bishops declared their agreement with Felix. A new synod convened at Frankfort (794) ratified the decrees of Ratisbon against adoptianism.

Finally, Archbishop Leidrad of Lyons prevailed upon Felix in 799 to appear before a synod at Aix-la-Chapelle, when, after a protracted discussion of the subject with Alcuin, he once more recanted. Felix was now committed to the charge of Leidrad at Lyons, where he died in 816. Elipandus never retracted his opinions, but soon after his death the sect became extinct. Adoptianism was the first important theological controversy concerning the person of Christ originating in the western church.