chief minister of the Holy Roman emperor Frederick II, distinguished as jurist, poet, and man of letters whose sudden fall from power and tragic death captured the imagination of poets and chroniclers, including Dante.

Born in the mainland part of the kingdom of Sicily to a poor family (his parents were said to have been beggars), he studied law at Bologna, apparently at the expense of that city. In 1221 the Archbishop of Palermo presented him to Frederick, who made him a court notary. From 1225 to 1234, he served as a judge in the Magna Curia (high court) of Sicily, in which role he became the principal author of the constitution of Melfi (1231), a legal code that systematized Norman law, superimposing the new Hohenstaufen absolutism. The code was written in the elegant Latin style for which Pietro became famous. An exponent of the rhetorical ars dictaminis (“craft of composition”), Pietro influenced the literary form of Frederick's letters and public documents and, through them, the rhetoric of European courts. As a poet, writing in both Latin and Italian, he played a part in the development of the dolce stil nuovo (“sweet new style”).

From 1230 on, Pietro was Frederick's closest adviser and most trusted ambassador. He undertook repeated missions to Popes Gregory IX and Innocent IV and in 1234 traveled to England to arrange a marriage between Frederick and Isabella, sister of Henry III. The emperor's collaborator and instrument in every important act of his reign, Pietro reached the apogee of his power in 1246, when he was appointed prothonotary (chief court official) and logothete (chancellor) of the kingdom of Sicily.

In 1249, however, Pietro was accused of plotting to poison the emperor. Arrested at Cremona, he was carried in chains from city to city until, finally, he was blinded at San Miniato, near Florence. It is not certain whether he died there from the injury or near Pisa by suicide. The question of the guilt of the man who, according to Dante, “held both keys of Frederick's heart” preoccupied contemporary writers, most of whom absolved him.