Eustachy Wołłowicz (Lithuanian: Eustachijus Valavičius; 1572–1630) was Bishop of Vilnius in 1616–1630. He was one of the more accomplished bishops of Vilnius in the 17th century. A son of the Protestant father and Eastern Orthodox mother, Wołłowicz became a Catholic and was educated at the Jesuit Academy of Vilnius and the Pontifical Gregorian University in Rome and was ordained as a priest. In 1600, Wołłowicz became a member of the Vilnius cathedral chapter and provost (praepositus) of Trakai. At the same time, entered the court of the Grand Duke Sigismund III Vasa becoming a referendary (a type of judge; 1600–1615), later royal secretary (1605–1615) and deputy chancellor (1615–1618). He was known as a skilled diplomat and politician. He became bishop of Vilnius after the death of in 161