Wikipedia:Selected anniversaries/April 18
- 1025 - Bolesław I the Brave was crowned in Gniezno, becoming the first King of Poland.
- 1506 - Construction of the current Saint Peter's Basilica in Vatican City, to replace the old Saint Peter's Basilica built in the 4th century, began.
- 1906 - A major earthquake (pictured) and subsequent fires devastated San Francisco, California, killing at least 3,000 and leaving more than half of the city's population homeless.
- 1947 - In the largest non-nuclear single explosive detonation in history, the Royal Navy set off 6,800 tonnes of surplus ammunition in an attempt to destroy Heligoland, Germany.
- 1980 - Rhodesia became the Republic of Zimbabwe, with Canaan Banana as the country's inaugural President and Robert Mugabe as the first Prime Minister.