upright=1.35|thumb|Emperor Lothair I divides Middle Francia between his three sons (Treaty of Prüm). __NOTOC__ Year 855 (DCCCLV) was a common year starting on Tuesday of the Julian calendar.
upright=1.35|thumb|Emperor Lothair I divides Middle Francia between his three sons (Treaty of Prüm). __NOTOC__ Year 855 (DCCCLV) was a common year starting on Tuesday of the Julian calendar