Peter Martyr Vermigli (8 September 1499 – 12 November 1562) was an Italian-born Reformed theologian. His early work as a reformer in Catholic Italy and his decision to flee for Protestant northern Europe influenced many other Italians to convert and flee as well. In England, he influenced the Edwardian Reformation, including the Eucharistic service of the 1552 Book of Common Prayer. He was considered an authority on the Eucharist among the Reformed churches, and engaged in controversies on the subject by writing treatises. Vermigli's Loci Communes, a compilation of excerpts from his biblical commentaries organised by the topics of systematic theology, became a standard Reformed theological textbook.

Born in Florence, Vermigli entered a religious order and was appointed to influential posts as abbot and prior. He came in contact with leaders of the Italian spirituali reform movement, and read Protestant theologians such as Martin Bucer and Ulrich Zwingli. Through reading these works and studying the Bible and the Church Fathers, he came to accept Protestant beliefs about salvation and the Eucharist. To satisfy his conscience and avoid persecution by the Roman Inquisition, he fled Italy for Protestant northern Europe. He ultimately arrived in Strasbourg where he taught on the Old Testament of the Bible under Bucer. English reformer Thomas Cranmer invited him to take an influential post at Oxford University where he continued to teach on the Bible. He also defended his Eucharistic beliefs against Catholic proponents of transubstantiation in a public disputation. Vermigli was forced to leave England on the accession of the Catholic Queen Mary. As a Marian exile he returned to Strasbourg and his former teaching position. Vermigli's beliefs regarding the Eucharist and predestination clashed with those of leading Lutherans in Strasbourg, so he transferred to Reformed Zürich where he taught until his death in 1562.

Vermigli's best-known theological contribution was defending the Reformed doctrine of the Eucharist against Catholics and Lutherans. Contrary to the Catholic doctrine of transubstantiation, Vermigli did not believe that the bread and wine are changed into Christ's body and blood. He also disagreed with the Lutheran view that Christ's body is ubiquitous and so can be physically present at the Eucharist. Instead, Vermigli taught that Christ remains in Heaven even though he is offered to those who partake of the Eucharist and received by believers.

Vermigli developed a strong doctrine of double predestination independently of John Calvin. His interpretation was that God's will determines both damnation as well as salvation. Vermigli's belief is similar but not identical to Calvin's. Vermigli's political theology was important in the Elizabethan religious settlement; he provided theological justification for royal supremacy, the doctrine that the king of a territory, rather than any ecclesiastical authority, rules the church.