James of Viterbo OSA (Italian: Giacomo da Viterbo; c. 1255 – c. 1307), born Giacomo Capocci (nicknamed Doctor speculativus), was an Italian Roman Catholic Augustinian friar and Scholastic theologian, who later became Archbishop of Naples.

James was born Giacomo Capocci in Viterbo in the Papal States around the year 1255.

He joined the Order of St. Augustine around the year 1272 at the monastery of the Most Holy Trinity in Viterbo.

[2] In September 1302, Pope Boniface VIII appointed him Archbishop of Benevento,[4] In December 1302, at the request of King Charles II of Naples, Capocci was transferred to the Archbishopric of Naples,[5] where he oversaw construction of the Cathedral of the Assumption of Mary.

In 1303 Capocci obtained his Doctor of Theology, and published the treatise, De regimine christiano (On Christian Government).