1070 (MLXX) was a common year starting on Friday of the Julian calendar, the 1070th year of the Common Era (CE) and Anno Domini (AD) designations, the 70th year of the 2nd millennium, the 70th year of the 11th century, and the 1st year of the 1070s decade. As of the start of 1070, the Gregorian calendar was 6 days ahead of the Julian calendar, which was the dominant calendar of the time.

• Hereward the Wake begins a Saxon revolt in the Fens of eastern England, which later collapses.
• Lanfranc, an Italian lawyer, becomes William's formidable Archbishop of Canterbury.
• Central Asian poet Yusuf Balasagun completes the Kutadgu Bilig.
• Bergen, Norway is founded by the king Olav Kyrre. This will function as the main city and capital of Norway, until it is replaced by Oslo in 1314.
• Abu Bakr Ibn-Umar founds Marrakesh.
• Chinese Chancellor Wang Anshi starts the Xining Reforms (which last until 1085).
• The Temple of Literature is established in the capital of Vietnam.
• A successful Byzantine counter-attack drives the Seljuk Turks across the Euphrates.
• Song Dynasty Chinese astronomer, engineer, and statesman Su Song completes the compilation of the Ben Cao Tu Jing, a pharmaceutical treatise with related subjects of botany, zoology, mineralogy, and metallurgy.

• Baldwin VI of Flanders (b. 1030)