1825 (MDCCCXXV) was a common yearstarting on Saturday of the Gregorian calendarand a common year starting on Thursday of the Julian calendar, the 1825th year of the Common Era (CE) and Anno Domini (AD) designations, the 825th year of the 2ndmillennium, the 25th year of the 19thcentury, and the 6th year of the 1820s decade. As of the start of 1825, the Gregorian calendar was 12 days ahead of the Julian calendar, which remained in localized use until 1923.

• January 4 – King Ferdinand I of the Two Sicilies dies and is succeeded by his son Francis I of the Two Sicilies.
• February 12 – The Creek cede the last of their lands in Georgia to the United States government, and migrate west
• March 4 – John Quincy Adams officially succeeds James Monroe as President of the United States.
• July 6 – The Duke of Schleswig-Holstein-Sønderborg-Beck gains possession of Glücksburg and changes his title to Friedrich Wilhelm, Duke of Schleswig-Holstein-Sonderburg-Glücksburg. The line of Schleswig-Holstein-Sonderburg-Glücksburg later became the Royal House of Greece, Denmark and Norway.
• July 30 – Malden Island (an uninhabited island in the central Pacific Ocean) discovered.
• August 6 – Bolivia gains independence from Peru as a republic with the instigation of Simón Bolívar
• August 25 – Uruguay declares independence from Brazil (See Uruguay's independence)
• September 27 – The world's first modern railway, the Stockton and Darlington Railway opens in England.
• October 26 – The Erie Canal opens – passage from Albany, New York to Lake Erie
• December 1 – Nicholas I of Russia succeeds his older brother Alexander I.
• Decembrist Revolt in Russia.
• The first horse-drawn omnibuses established in London
• First roller skates
• Aluminium discovered
• City of Brisbane founded – see History of Brisbane
• The electromagnet was invented by William Sturgeon

• May 2 – Michail Leontievich Bulatov, Russian military