- 1403 21 Jul Henry IV defeats Henry Percy ('Hotspur'), a rebel and ally of Owain Glyndwr, at the Battle of Shrewsbury.
- 1588 21 Jul The Armada - an invasion fleet sent by Philip II of Spain - is sighted off the coast of Cornwall.
- 1969 21 Jul US astronaut Neil Armstrong becomes the first man to walk on the moon, stepping down from Apollo 11.

