Google's DeepMind AlphaGo artificial intelligence has defeated the world's number one Go player Ke Jie.
AlphaGo secured the victory after winning the second game in a three-part match.
DeepMind founder Demis Hassabis said Ke Jie had played "perfectly" and "pushed AlphaGo right to the limit".
Following the defeat, Ke Jie told reporters: "I'm a little bit sad, it's a bit of a regret because I think I played pretty well."
In Go, players take turns placing stones on a 19-by-19 grid, competing to take control of the most territory.
It is considered to be one of the world's most complex games, and is much more challenging for computers than chess.