Motiejus Kazimieras Valančius (Lithuanian pronunciation: [moːtiː.əjʊsʲ vɐɫɐŋtʃjʊsʲ]; Polish: Maciej Kazimierz Wołonczewskiⓘ,[1] also known by his pen-name Joteika and Ksiądz Maciek;[2] 1801–1875) was a Catholic Bishop of Samogitia, historian and one of the best known Lithuanian/Samogitian writers of the 19th century.

Having been absent from Lithuania during the anti-Russian uprising in 1831, Valančius was considered to be relatively apolitical, and thus the Russian government did not object when he was proposed as an Episcopal candidate for the see of Samogitia.

He expanded and improved the Samogitian parochial school network, wrote many religious books, and in 1858 inaugurated a temperance movement, which grew to encompass nearly a million members, almost half of the county’s population.

His pastoral and educational work was interrupted by the uprising of 1863–1864 and was made extremely difficult as the Russian government tightened its reins after the revolt's defeat.

As an educator, able Church administrator, historian and ethnographer, and talented writer, Valančius is one of the most versatile and influential figures in 19th-century Lithuania.