Der 100. Psalm (The 100th Psalm), Op. 106, is a composition in four movements by Max Reger in D major for mixed choir and orchestra, a late Romantic setting of Psalm 100. Reger began composing the work in 1908 for the 350th anniversary of Jena University. The occasion was celebrated that year with the premiere of PartI, conducted by Fritz Stein on 31July. Reger completed the composition in 1909. It was published that year and premiered simultaneously on 23February 1910 in Chemnitz, conducted by the composer, and in Breslau, conducted by Georg Dohrn.
In 1922, the biographer Eugen Segnitz noted that this work, of intense expression, was unique in the sacred music of its period, with its convincing musical interpretation of the biblical text and manifold shades of emotion. Paul Hindemith wrote a trimmed adaption which probably helped to keep the work in the repertory, and François Callebout wrote an organ version, making the work accessible for smaller choirs. The organ version was first performed in 2003, in Wiesbaden where the composer studied. The celebration of the Reger Year 2016, reflecting the centenary of the composer's death, led to several performances of Der 100. Psalm.
Born in Bavaria in 1873, Reger studied at the Wiesbaden Conservatory and worked as a concert pianist and composer. His work focused first on chamber music, Lied, and choral music. In 1898, after he completed his studies, he returned to his parental home and focused on works for organ, continuing the tradition of Johann Sebastian Bach. Though raised as a Catholic, he was inspired by Lutheran hymns, writing chorale fantasias such as 40, in 1899. He moved to Munich in 1901. In 1902 he married Bercken, a divorced Protestant. In 1907 Reger was appointed professor at the Royal Conservatory in Leipzig. A year later he began the setting of Psalm 100 with the first movement.