Finlandia, Op. 26, is a tone poem by the Finnish composer Jean Sibelius. It was written in 1899 and revised in 1900. The piece was composed for the Press Celebrations of 1899, a covert protest against increasing censorship from the Russian Empire, and was the last of seven pieces performed as an accompaniment to a tableau depicting episodes from Finnish history.
In order to avoid Russian censorship, Finlandia had to be performed under alternative names at various musical concerts. Titles under which the piece masqueraded were numerous—famous examples include Happy Feelings at the awakening of Finnish Spring, and A Scandinavian Choral March.
As a hymn, it’s called Be Still My Soul.