|Centuries:||10th century – 11th century – 12th century|
|Decades:||1010s 1020s 1030s – 1040s – 1050s 1060s 1070s|
|Years:||1037 1038 1039 – 1040 – 1041 1042 1043|
- March War of Independence of Western Xia occurred.
- June 17 – Harthacanute lands at Sandwich and reclaims the English Throne.
- August 15 – King Duncan I is killed in battle against his first cousin and rival Macbeth. The latter succeeds him as Scottish Monarch.
- The oldest brewery still active is founded at Weihenstephan.
- Seljuk Turks defeat the Ghaznavids at the Battle of Dandanaqan.
- February 22 – Rashi, French rabbi and commentator (d. 1105)
- June 27 – King Ladislaus I of Hungary (d. 1095)
- King Alfonso VI of Castile, Spanish royal (died 1109)
- March 17 – Harold Harefoot, King of England
- August 15 – King Duncan I of Scotland (b. 1001)
- October 1 – Alan III, Duke of Brittany (poisoned) (b. 997)
- For the U.S. Internal Revenue Service (IRS) form, see Form 1040.