Ernst I von Tonna

Ernst I (c. 1096 – 29 December 1151) was the elder son of Count Erwin I of Gleichen and Helinburg of Lohra. He appears as count of Tonna in 1110 and count in Thuringia in 1114, and from 1120 he held the advocacy of Erfurt.

Charters show him as Vogt of the abbeys of Erfurt and Gerode and as burgrave-count of Harburg in the Eichsfeld. He died on 29 December 1151, and by an unnamed wife left sons Erwin II and Ernst II.