Christian I of Buch (c. 1130 - 23 August 1183) was the Archbishop of Mainz from 1160 until 1161, and again from 1165 until 1183.

Christian was born into the noble families of Buch and Beichlingen. Christian's greatest supporter was Duke Louis IV of Thuringia, who helped him obtain the position of a cathedral provost in Merseburg and a provost in Mainz. In 1160 the Archbishop of Mainz, Arnold of Selenhofen, was murdered in a mob, and the citizens of the city elected Rudolph of Zähringen his successor. However some members of the cathedral fled to Frankfurt and elected Christian his successor, beginning a schism. However the Holy Roman Emperor Frederick I Barbarossa recognised neither of the two candidates and with the support of Pope Victor IV at the Council of Lodi on 20 June 1161 both were deposed in favour of Conrad I of Wittelsbach.

In consequence, Christian was made a provost of the cathedral of Mainz and the provost of St Servaas in Maastricht in 1162. He accompanied Frederick Barbarossa on his third Italian campaign in 1163. In 1165 Conrad of Wittelsbach broke with the emperor and recognised Pope Alexander III instead of the Antipope Paschal III, which led Frederick to depose Conrad and promote Christian to the archbishopric. In 1167 Christian accompanied Frederick on his fourth Italian campaign, and while on it he received his priestly and bishops confirmations. On 29 May 1167 Christian and Raynald of Dassel, Archbishop of Cologne, defeated a papal army at Tusculum, anf Frederick entered into Rome victorious. But there was soon an outbreak of malaria in the army which killed Raynald, and Christian succeeded him as Imperial Arch-Chancellor.

In 1168 Christian mediated the conflict between the kings of England and France in Rouen, and he also mediated the dispute between Frederick Barbarossa and Duke Henry the Lion of Saxony. Christian was also active in trying to end the papal schism, and he led his armies against Guelphs in northern Italy. In 1177 he mediated between Pope Alexander III and Frederick at the Peace of Venice, which induced the Pope to grant Christian the pallium and recognise him. In March 1179 he took part in the Council of the Lateran. He died and was buried in Tusculum in 1183.

Preceded by:

Christian I of Buch

Succeeded by:

Rudolph of Zähringen Archbishop of Mainz
1160 - 1161
opposed... Rudolph of Zähringen
1160 - 1161
Conrad I of Wittelsbach
Conrad I of Wittelsbach Archbishop of Mainz
1165 - 1183
Conrad I of Wittelsbach