Wilhelm Rein (10 August 1847, Eisenach - 19 February 1929, Jena) was a German educational theorist.
Rein studied theology (and pedagogy under Karl Volkmar Stoy) in Jena, going on to Tuiskon Ziller at Leipzig. In 1871 he became a teacher at Friedrich Wilhelm Dörpfeld's school in Barmen, in 1872 a teacher in Weimar, and moved to Eisenach in 1876. In 1886 he was appointed professor in Jena. Rein was a late representative of the Herbartian school. One of his students was Hermann Lietz.