Otto IV, Count of Weimar-Orlamünde

Otto IV, in some sources numbered Otto VI (born before 1279, died 1318), was count of Weimar-Orlamünde, the son of Otto III and Agnes of Truhendingen. Before 1296 he married Adelaide of Käfernburg, who bore his heir, Otto VI.

After her death he married Catherine of Hesse in 1308; their daughter Elizabeth married Count Henry X of Schwarzburg. Otto died in 1318.