The Roman Catholic (soon Metropolitan) Archdiocese of Mohilev (or Mogilev or Mahilyow) was a territorial division of the Roman Catholic Church, covering a significant (western) proportion of the territory of the Czarist Russian empire.
It was erected as Diocese of Mohilev in 1772 by the Russian empress Catherine the Great, in a unilateral action independent of Rome. Its territory was split off from the Dioceses of Inflanty and Smolensk. Its initial see was the imperial capital city Saint Petersburg.
In 1782 Catherine elevated the diocese to an Archdiocese, and in 1783 these actions were recognised by Pope Pius VI in the bull Onerosa pastoralis officii.
On 9 August 1798, it lost territory to establish the Diocese of Minsk (in Belarus); the same year it was raised to Metropolitan rank. The archdiocese remained the Latin Metropolitan see for Russia throughout imperial times and the Soviet period, although for much of the latter period it was the subject of repression and had no incumbent archbishop.
In 1818 it gained territory from the suppressed Diocese of Smolensk.
It repeatedly lost territory, to establish successively the Cherson on 3 July 1848, the Apostolic Exarchate of Russia in 1917, the Diocese of Riga on 22 September 1918, the Apostolic Vicariate of Finland on 8 June 1920 and the Apostolic Vicariate of Siberia on 1 December 1921.