1451 (MCDLI) was a common year starting on Friday of the Julian calendar, the 1451st year of the Common Era (CE) and Anno Domini (AD) designations, the 451st year of the 2nd millennium, the 51st year of the 15th century, and the 2nd year of the 1450s decade. As of the start of 1451, the Gregorian calendar was 9 days ahead of the Julian calendar, which was the dominant calendar of the time.

• February 3 – Murad II, Sultan of the Ottoman Empire dies and is succeeded by his son Mehmed II.
• April 11 – Celje acquires market-town status and town rights by orders from the Celje count Frederic II.
• June 30 – French troops under the Comte de Dunois invade Guyenne and capture Bordeaux
• August 20 – The French capture Bayonne, the last English stronghold in Guyenne
• Foundation of the University of Glasgow
• Nicholas of Cusa invents concave lens spectacles to treat myopia
• Roger van der Weyden paints his Last Judgement
• Lodi dynasty succeeded the Sayyid dynasty in India

• Christopher Columbus
• April 22 – Isabella of Castile