Pietro Igneo (died 11 November 1089) was an Italian Roman Catholic Benedictine monk from the Vallombrosians branch.

The Vallombrosian monks were his chief accusers and upon the insistence of the people for proof the judgment of God - or a trial through fire - was resorted to settle the matter.

The abbot (and his relative) John Gualbert designated for the test Pietro who underwent the ordeal on 23 February 1068 (he succeeded) and was hence called "Igneo" which meant "fire-tried".

[5] Gregory VII entrusted him with several important missions: in 1079 he served as a papal legate in the German kingdom with the Bishop of Padua to mediate between the Emperor Henry IV and Rudolf of Swabia.

[4] Upon the renewal of the excommunication against the emperor at Salerno in 1084 he was designated - at Pope Gregory VII's behest - as one of the two legates sent to France for the promulgation of the sentence.