Bishop Joseph Toal is leaving his diocese of Argyll and the Isles to replace Joseph Devine as Bishop of Motherwell.
The 58-year-old has been Apostolic Administrator of the South Lanarkshire diocese since June last year and will now take over the role permanently.
Bishop Devine tendered his resignation in August 2012 on his 75th birthday but continued in his post for 10 months as no successor was appointed.
He became a bishop in 1977 and took the role in Motherwell in May 1983.
Regarding the move, Bishop Toal said: "While I am sad to be leaving my home diocese of Argyll and the Isles, I know the deep faith of the people there will sustain them as they await a new bishop."
Archbishop Philip Tartaglia, president of the Bishops' Conference of Scotland, added: "I wish him every blessing in his new appointment."