Ferdinand August Rojahn (1822-1900) was a German-born organist, violinist and conductor.
The son of Johan Friedrich Gottlieb Rojahn and Dorothea Schunnemann Rojahn, Ferdinand August Rojahn was born in Bad Gandersheim, Germany in 1822. He was educated as a musician in the cities of Hildesheim and Hamburg. In the latter city he was a pupil of Carl Schwencke, the son of Christian Friedrich Gottlieb Schwencke.
In 1841 Rojahn joined the Harz-Verein, a German orchestra which traveled to Norway and performed more than 340 concerts on tour in that nation in 1840-1841. That orchestra settled into residency at the Christiania Theatre where Rojahn was employed as a conductor of operas. In addition to conducting he also played in the orchestra at that theatre from 1841-1845.
Rojahn was employed by the city of Fredrikstad as a town musician from 1845-1853. He was a violin and piano teacher to the Norwegian composer, violinist and conductor Sigurd Lie (born 1871). He taught Lie while serving as organist at the Kristiansand Cathedral; a post he held in 1853-1854. He was principal conductor of Musikselskabet Harmonien (which later became the Bergen Philharmonic Orchestra) from 1856 until 1859.
In 1859 Rojahn married to Birgitte Cornelia Gulbrandsen (1839-1927). They had 8 children; two of which became professional musicians. He died in 1900.