Arnold I may refer to:
Clergy Arnold I of Cologne (c. 1100–1151), the Archbishop of Cologne 1137–1151 Arnold I of Vaucourt (c. 1120–1183), the Archbishop of Trier 1169–1183 Arnold I van Isenburg (died c. 1197), the Bishop of Utrecht 1196–1197 Arnold I (bishop of Coria) (died 1197/98), a Catholic bishop in Spain Arnold I (bishop of Poznań) (died 1211), a Catholic bishop in Poland
Nobility Arnold I of Astarac (died 960), the first Count of Astarac from 926 Arnold I, Count of Chiny (died 1106), son of Louis II Arnold I, Count of Loon (c. 1050–c. 1130), son of Emmo Arnold I, Count of Cleves, the Count of Cleves 1119–1147 Arnold I, Count of Laurenburg (died before 1154) Arnold I, Lord of Egmond (c. 1337–1409), Lord of Egmond and IJsselstein