Gerard I of Dhaun (? - 25 September 1259) was the Archbishop of Mainz from 1251 until 1259. Gerard was a member of the house of the Wildgraves of Dhaun and Kyrburg. Gerard had a career in the cathedral of Mainz before he left it in 1244 after he refused to follow the anti-Hohenstaufen policy of the then archbishop Siegfried III of Eppstein. In 1249 he reconciled with Siegfried and joined him. After Christian II of Bolanden was paid to leave the archbishopric by Pope Innocent IV, Gerard was elected the new Archbishop of Mainz. Once elected, however, Gerard took a pro-Hohenstaufen policy and supported King Conrad IV.