Joseph Werth SJ (Russian: Иосиф Иоганнович Верт; born October 4, 1952, in Karaganda, Kazakhstan) is a Russian-German Roman Catholic prelate who has been the Bishop of Transfiguration in Novosibirsk since 2002.

Named as the Latin Church Apostolic Administrator of Siberia—a see that encompassed 4.2 million square miles (10.3 per cent of all the land on earth) and extends through nine of the world's twenty four time zones—by Pope John Paul II on April 13, 1991, Werth initially had only two Ukrainian-born priests to help him minister to an estimated 500,000 Catholics.

Joseph Werth began studies for the priesthood clandestinely in Lithuania under the direction of a leader of the underground Jesuits, who also secretly accepted him into the Lithuanian Province of the Society of Jesus.

The Bishop's paternal grandfather was Joseph Werth, who was born in 1871 at Schoenchen [1], Russian Empire and deported as a kulak to Kazakhstan in 1929 (with his wife and children).

The Bishop's maternal grandfather was Dominic Hoerner (born near Odesa, Ukraine), who was deported around 1931 to Kazakhstan with his family.