Irminsul was an oak venerated by the heathen Saxons and which was said to connect heaven and earth. The Old Norse form of Irmin was Jörmun and interestingly, just like Ygg, it was one of Odin's names. Yggdrasil was the yew or ash tree from which Odin sacrificed himself, and which connected heaven and earth. It appears, thus, that Irminsul may have represented a World tree corresponding to Yggdrasil among the Saxon tribes of Germany.

Allegedly it was located near Eresburg castle, Paderborn. According to legend the Irminsul was destroyed by Charlemagne, in 772.