May 23: Victoria Day in Canada (2005)
- 1533 - The marriage of Catherine of Aragon and Henry VIII of England was annulled.
- 1568 - The Eighty Years' War broke out when Dutch rebels led by Louis of Nassau invaded Friesland in the Battle of Heiligerlee.
- 1873 - The North West Mounted Police was established in the Northwest Territories, Canada.
- 1934 - American bank robbers Bonnie and Clyde were ambushed by police and killed in Black Lake, Louisiana.
- 1969 - British rock band The Who released the rock opera Tommy.