Wikipedia:Selected anniversaries/August 18
- 293 BC – The oldest known Roman temple to Venus was founded, starting the institution of Vinalia Rustica.
- 1572 – French Wars of Religion: Marguerite de Valois (pictured) was married to Huguenot King Henry of Navarre, in a supposed attempt to reconcile Protestants and Catholics in France.
- 1590 – John White, the governor of the Colony of Roanoke, returned from a supply trip to England and found his settlement deserted.
- 1868 – Pierre Janssen discovered helium while analyzing the chromosphere during a total eclipse of the sun. This was the first element detected in space before being found on Earth.
- 1941 – The T-4 Euthanasia Program in Nazi Germany was temporarily halted due to public resistance.
- 1966 – Vietnam War: A company of the Royal Australian Regiment fought a much larger North Vietnamese unit in the Battle of Long Tan.
More events on this day... Recent days: August 17 – August 16 – August 15