Year 91 (XCI) was a common year starting on Saturday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Glabrio and Traianus (or, less frequently, year 844 Ab urbe condita). The denomination 91 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.

Year 91 (XCI) was a common year starting on Saturday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Glabrio and Traianus (or, less frequently, year 844 Ab urbe condita). The denomination 91 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.