Otto of Tonengo[a] (c. 1190 – 1250/1251) was an Italian papal diplomat and cardinal, first as deacon of San Nicola in Carcere from 1227 and then as bishop of Porto e Santa Rufina from 1244.
In 1229–1231, he travelled extensively through France, the Low Countries, Germany, Denmark and Norway on Papal business.
Otto was born at Tonengo in the Piedmont, between about 1180 and 1200, into a family closely linked to the nobility of Cocconato and Cavagnolo and to the Fieschi of Genoa.
His family was among the feudatories of the Marquisate of Montferrat, but he was not a blood relative of Marquis William III, as sometimes alleged.
In 1224, he was studying law at the University of Bologna when he was sent before Pope Honorius III to protest on behalf of the school the regulations imposed by the podestà and comune.
[2] After his return to Rome, Otto witnessed a testamentary codicil of a fellow Piedmontese, Cardinal Guala Bicchieri.
He was appointed cardinal deacon of San Nicola in Carcere by Pope Gregory IX on 18 September 1227, a little over two years since entering the Papal chancery.
In December 1227, he was sent with Cardinal Thomas of Capua on a secret mission to the Frederick II, Holy Roman Emperor.
In 1229, he issued statutes for the reform of the Benedictines and Augustinians in Alsace, and between December 1229 and May 1230 he helped organize a new religious order, the Penitent Sisters of Saint Mary Magdalene in Germany.
[2] Early in 1232, Gregory IX sent Otto with Cardinal James of Pecorara to northern Italy to negotiate a peace between the warring factions of the Guelphs and Ghibellines, the latter the allies of Emperor Frederick II.
When in July 1237 he came to Osney Abbey, a brawl broke out between a group of scholars from the university and the cardinal's men in which the legate's cook was killed.
Otto himself was locked for safety in the abbey tower, emerging unscathed to lay the city under interdict in reprisal.
[2] After the death of Gregory IX on 21 August 1241, the College of Cardinals persuaded Frederick II to allow Otto and James to participate in the election of a successor provided that afterwards they return to prison.
[2] Freed at some point, Otto was transferred by Innocent IV from the diaconate of San Nicola to the bishopric of Porto e Santa Rufina on 28 May 1244.
On the eve of the First Council of Lyon, Innocent dispatched him to Germany to negotiate peace with Frederick II and to regularize the Humiliati, a new religious movement.