Oleg's treaty with Byzantium
The oldest surviving treaty between Rus' and another power

After his campaign against Constantinople, Prince Oleg won a treaty giving Rus' merchants duty-free trade and upkeep in the city. The text survives in the Primary Chronicle and is the oldest record of Rus' law.
Wikipedia (Russian) · Wikipedia (English) · 10th century
Meanwhile around the world (±25 years)
Africa
- c. 900 The bronzes of Igbo-Ukwu — 11 years earlier
Americas
- c. 900 Rise of Chichen Itza — 11 years earlier
Alive at the time
- Oleg the Wise (aged 66)
- Igor of Kiev (aged 33)
- Æthelstan (aged 17)
- Edward the Elder (aged 37)