Juhana "Johan" Fredrik Cajan (13. September 1815 - 28. February 1887) was a Finnish reverend and historian. He was born in Sotkamo, Finland and died in Piippola, Finland.Cajan's parents were Johann Cajan and Eva Elfving. After his exam he traveled to Lapland. During his studies, he got to know Elias Lönnrot, and he collected folklore with him. Cajan wrote about Finland's history (in the Finnish language) in the publication Mehiläinen 1839-40. He used writing names as J.F. Kainonen and J.F.