Paulus Petri Juusten (Finnish: Paavali Juusten, Swedish: Paul (Påvel) Pedersson Juusten; ca. 1516/1520 at Juustila near Viborg, Sweden (now Vyborg, Russia) – 22 August 1575 in Åbo, Sweden (now Turku/Åbo, Finland) was the first bishop of Vyborg, and later, bishop of Turku. He was an esteemed teacher and a Swedish royal envoy.
Paavali, as he was known before ecclesiastical career, was initially schooled at the Viborg School of Latin. His parents, burgher Pietari Juusten and his wife Anna, owned their townhouse near the Blackfriars' monastery at Viborg. The street bore the name Juusteninkatu until the town centuries later was ceded to the Soviet Union. His parents seemingly died in ca. 1530 due to the plague. The orphan Paavali was sent to Turku, to study 1534–1536 at the Turku school. He was recruited to lecture as an assistant to the head teacher, bishop Martti Skytte. The bishop ordained Paulus as a priest in 1540, before he turned 24 that was the regularly required age for ordination.
Juusten was acting headmaster of the Viborg school 1541–1543, after which the bishop sent him to Germany, to study in several universities. He succeeded Mikael Agricola as headmaster of Turku cathedral school in 1548. He was member of the diocese chapter in 1553 and in 1554. In 1554 he was appointed as the inaugural bishop of Viborg, a new diocese. He was consecrated as bishop by Botvidus Sunonis, bishop of Strengnes, a carrier of the apostolic succession. In 1563 he succeeded as bishop of Turku. The king sent bishop Juusten as ambassador to Russia in 1569, where tsar Ivan IV the Terrible kept him as a prisoner for over two years. Some sources claim that he received ennoblement from the king after his return in ca. 1573. The year he died, Paulus consecrated Laurentius Petri Gothus as archbishop of Uppsala. He was buried at the Cathedral of Turku.