The Cajanus family is an ancient Finnish clerical family that has produced numerous clergymen, government officials, and academics. Count Per Brahe nominated the progenitor of the family, a local nimismies Anders Eriksson (Hjerta), to serve as bailiff of his fiefdom of Kajaani. His sons became pastors in neighbouring parishes and the family assumed a Latinate surname derived from the name of the town of Kajaani.
Members of this family include:
- Daniel Cajanus (1703–1749) a world-famous giant who was a member of royal courts and performed in England and Holland.
- Juhana Cajanus (1655–1681), professor and hymnwriter, graduated with an M.A. from Uppsala in 1679, appointed as professor of philosophy at Turku Academy in 1680.
- Erik Cajanus (1658–1723), Priest of Paltamo
- Juhana Fredrik Cajan (1815–1887), historian
- Robert Kajanus (1856–1933), Finnish conductor and composer
- Werner Cajanus (1878–1919), professor and inventor, first professor of forest inventory in Finland
- Korhonen, Lauri. "Researcher". University of Eastern Finland. Retrieved 26 July 2012.
- Bondeson, Jan. The Two-Headed Boy and Other Medical Marvels. Ithaca: Cornell, 2000.