Ruthard (died 1109) was Archbishop of Mainz from 1089 to 1109, and a leading opponent of the Emperor Henry IV and his antipope Clement III (Wibert of Ravenna).

[5] At a diet held in Hardenburg (85 km south of Mainz) in 1098, Archbishop Ruthard was accused by some courtiers before Emperor Henry IV, whom he opposed in the Investiture Conflict, of appropriating property of murdered Jews.

Perceiving that he was losing the good will of the emperor, Ruthard departed from Mainz secretly at night, and headed into Thurungia, where he spent several years in exile.

[6] The antipope Clement III called Ruthard's actions thievery, in a letter of 29 July 1099 written to the Provost, clergy and people of Mainz.

He obtained the cooperation of all the suffragan bishops of the ecclesiastical province of Mainz, and then had the (schismatic) papal legate, Cardinal Rupert (Robert),[9] antipope Clement III's apocrisiarius, consecrate the candidate, Hermann, on 8 April 1100.

He was unsuccessful, but in late July or early August the old emperor requested his son to dismiss his army and come to Ingelheim to a colloquy, at which, among others, he wanted the archbishop of Mainz to be present.

[13] Henry V, having made satisfactory arrangements with the ecclesiastical authorities, suspended the remaining supporters of Clement III and his successors, and required them to undergo an examination by Pope Paschal II.

[17] In 1108, Archbishop Ruthard refounded Disibodenberg Abbey, at the place where Disibod had built a cell at the confluence of the rivers Nahe and Glan, by replacing the college of canons with regular monks.