On this day in history July 21,
- 1970 – After 11 years of construction, the Aswan High Dam in Egypt is completed.
- 1972 – The Troubles: Bloody Friday – the Provisional IRA detonate 22 bombs in central Belfast, Northern Ireland, United Kingdom in the space of 80 minutes, killing nine and injuring 130.
- 1973 – In the Lillehammer affair in Norway, Israeli Mossad agents kill a waiter whom they mistakenly thought was involved in the 1972 Munich Olympics Massacre.
- 1976 – Christopher Ewart-Biggs, the British ambassador to the Republic of Ireland, is assassinated by the Provisional IRA.
- 1977 – The start of the four day long Libyan–Egyptian War.
- 1983 – The world’s lowest temperature in an inhabited location is recorded at Vostok Station, Antarctica at −89.2 °C (−128.6 °F).
- 1995 – Third Taiwan Strait Crisis: The People’s Liberation Army begins firing missiles into the waters north of Taiwan.