Saint Theonestus of Vercelli is venerated as a martyr by the Catholic Church. Theonestus may have been a member of the early Christian community in Vercelli, living in an era earlier than that of Eusebius of Vercelli. Theonestus may have been a martyr, whose relics were buried in the cemetery where other Christians were buried, outside the city walls. It is believed that his whole body was conserved in the tomb dedicated to him. He is probably not the saint of the same name who was said to have been killed at Altinum by the Arians. This saint of Altinum, whose legend, in any case, is confused and contradictory, may have been confused for the martyr of Vercelli, whose historicity is more certain.