HAITO (HATTO). - Bishop of Basel, born into a noble Swabian family in 763. At the age of five he was received into the monastery of Reichenau, where he made such great progress in his studies that Abbot Waldo (786-806) placed him in charge of the monastic school. When the latter was transferred in 806 to the Parisian abbey of S. Dionigi, H. succeeded him; but almost at the same time he was made bishop of Basel.
He showed great zeal in rebuilding the Cathedral and reforming the clergy; he also rebuilt the abbey church of Reichenau. Charlemagne, who held him in high esteem, entrusted him in 811 with a diplomatic mission to Constantinople. Owing to illness, in 823 he resigned his two offices of bishop and abbot and spent the rest of his days as a simple monk at Reichenau, where he died on 17 March 836.
He wrote several works, including the Hodoeporicon, a kind of diary of his mission to the East; the Libellus de visione et obitu Wetini monachi Angiensis (PL 105, 771-80;
MGH, Poetae Latini medii aevi. Poetae Latini aevi Carolini, II, pp. 267-75), which might rank among the sources of the Divina Commedia; and the Capitulare of his diocese (PL 105, 763-68; MGH, Legum Sectio II Capitularia Regum Francorum, I, pp. 363-66; Mansi, XIV, 393-98).