AlphaGo has defeated South Korean Go champion Lee Se-dol in the first match of the landmark games between man and artificial intelligence (AI).
It was the first match out of a total of five between Lee and Google DeepMind's AI, taking place at the Four Seasons Hotel in Seoul.
DeepMind's Aja Huang stood in for AlphaGo across from Lee to place the pieces. The game was tense throughout, with both the AI and the 33-year-old playing aggressively. Commentators and professionals at the hotel said it was impossible to predict who would win during the match.
Lee looked nervous throughout the game, but smiled once in the middle, when he seemed to be amused by AlphaGo's surprising skills and aggressiveness.
The game was even until mid game, but AlphaGo took the edge near the end of the match. After 186 turns, Lee shook his head and surrendered.
It is the first time that a computer has defeated a Go player ranked 9-dan, the highest skill level for the game.
For the live stream on YouTube, around 95,000 viewers tuned in simultaneously for the English commentary version, and 56,000 for the Korean version near the end of the game.
Korean commentators expressed their shock at the defeat, and praised AlphaGo's sophisticated play.
DeepMind CEO Demis Hassabis tweeted mid-game: "extremely tense... Lee Sedol is famous for his creative fighting skills, AlphaGo going toe to toe. Incredibly complicated position."
Go is a Chinese board game played by two players alternatively placing black and white playing pieces, with the goal to surround more territory than your opponent. Your opponent's stones can be removed by surrounding them with yours.
Commentator Michael Redmond, an American 9-dan champion himself, said AlphaGo was playing at a professional level, and has improved dramatically since his last match.
Alphabet executive chairman Eric Schmidt, who is visiting Seoul to watch the match, called the match "a win for humanity" in a press conference.
AlphaGo defeated a European Go champion 5-0 last October.
The second round commences tomorrow.