Europa
- 1506: End of the Lisbon Massacre, with over 1,900 suspected Jews killed by Portuguese Catholics.
- 1509: Death of King Henry VII of England; succeeded by his son, Henry VIII.
- 1526: First Battle of Panipat – Babur defeats and kills Ibrahim Lodi, ending the Lodi dynasty (event in India but with major European dynastic consequences).
- 1782: Founding of Rattanakosin (Bangkok), by King Buddha Yodfa Chulaloke (not Europe, but noted in European sources).
- 1789: John Adams sworn in as the first Vice President of the United States (important for European-American relations).
- 1796: Napoleon Bonaparte decisively defeats the Piedmontese at the Battle of Mondovi, turning the Italian campaign in France’s favor.
- 1809: Napoleon’s forces drive two Austrian corps from Landshut on the first day of the Battle of Eckmühl (Napoleonic Wars).
- 1836: Battle of San Jacinto – Texas forces defeat Mexico (not Europe, but relevant to European powers’ interests).
- 1856: Australian labor movement: Stonemasons march for the eight-hour workday (influenced by European labor trends).
- 1894: Norway adopts the Krag–Jørgensen rifle as its main military arm.
- 1898: Spanish–American War: The US Navy begins a blockade of Cuba; the war declaration is retroactively dated to April 21.
- 1918: Manfred von Richthofen (“The Red Baron”), German WWI flying ace, is shot down and killed over France.
- 1926: Birth of Queen Elizabeth II in London.
- 2002: First round of French presidential elections; Jacques Chirac faces Jean-Marie Le Pen.
America
- 1794: New York City declares Ellis Island publicly owned to build forts for defense against the British.
- 1836: Battle of San Jacinto – Texan forces led by Sam Houston defeat the Mexican army, securing Texas independence from Mexico.
- 1878: First Lady Lucy Hayes begins the tradition of the White House Easter egg roll.
- 1914: Ypiranga Incident – The U.S. Navy intercepts a German arms shipment to Mexico near Veracruz.
- 1970: First Earth Day is celebrated in the United States, helping to launch the modern environmental movement.
- 1995: The FBI arrests Timothy McVeigh for the Oklahoma City bombing.
- 1972: Apollo 16 lunar module lands on the Moon (U.S. mission).
Asia
- 1451: Bahlol Khan Lodi becomes the ruler of Delhi, founding the Lodi dynasty in India.
- 1526: Death of Ibrahim Lodi in the First Battle of Panipat, marking the beginning of Mughal rule in India.
- 1879: Birth of R.A. Kartini, Indonesian national heroine and pioneer for women’s rights.
- 1938: Death of Allama Muhammad Iqbal, renowned philosopher and poet in Pakistan.
- 1987: Over 100 people die in a bomb blast in Colombo, Sri Lanka.
- 1989: Around 100,000 students gather in Tiananmen Square, Beijing, to commemorate reform leader Hu Yaobang, marking a key moment in the Tiananmen Square Protests.
- 2006: The King of Nepal announces the handover of power to the elected government.
- 2021: Indonesian Navy submarine KRI Nanggala sinks in the Bali Sea during a military drill, with all 53 crew members lost.
Africa
- 1997: Kenyan athlete Lameck Aguta wins the 101st Boston Marathon, marking a significant achievement for African runners on the international stage.
- World Creativity and Innovation Day: April 21 is observed as World Creativity and Innovation Day, recognized by the United Nations and celebrated across Africa and globally.
This day in history: 21 april