Juhana "Johan" Fredrik Cajan (13 September 1815 – 28 February 1887) was a Finnish clergyman and historian, the author of the first history of Finland written in Finnish.
Cajan wrote about Finland's history (in the Finnish language) in the publication Mehiläinen 1839-40.
His magnum opus is Suomen Historia, koetteeksi kerrottu lyhykäiset järjestyksessä.
Cajan wrote the first non-fiction literature in Finnish.
[citation needed] In 1842 Cajan married Adolfina Augusta Tauler (died 1858).