1798 (MDCCXCVIII) was a common year starting on Monday of the Gregorian calendar and a common year starting on Friday of the Julian calendar, the 1798th year of the Common Era (CE) and Anno Domini (AD) designations, the 798th year of the 2nd millennium, the 98th year of the 18th century, and the 9th year of the 1790s decade. As of the start of 1798, the Gregorian calendar was 11 days ahead of the Julian calendar, which remained in localized use until 1923.