The Roman Catholic Diocese of De Aar (Latin: De Aaren(sis)) is a diocese located in the city of De Aar (Pixley ka Seme District Municipality) in the ecclesiastical province of Cape Town in South Africa.

• March 24, 1953: Established as Apostolic Prefecture of De Aar from Diocese of Aliwal
• April 13, 1967: Promoted as Diocese of De Aar

• The cathedral is Cathedral of Our Lady of the Assumption in De Aar.

• Prefect Apostolic of De Aar (Roman rite)
  • Fr. Louis Dettmer (1953.03.24 – 1967.04.13)
• Bishops of De Aar (Roman rite)
  • Bishop Joseph Anthony De Palma, S.C.I. (1967.04.13 – 1987.11.18)
  • Bishop Joseph James Potocnak, S.C.I. (1992.01.23 - 2009.07.17)
  • Bishop Adam Leszek Musialek, S.C.I. (since 2009.07.17 - )

• Roman Catholicism in South Africa
• www.diocesedeaar.com

• GCatholic.org
• Catholic Hierarchy

30°39′S 24°01′E / 30.650°S 24.017°E / -30.650; 24.017