Google's Go playing program scored its final victory against South Korean Grand Master Lee Sedol, ending the five-game battle with four wins. The software was awarded an honorary 9-dan title, the highest rank in Go.
Lee resigned after five hours of play on Tuesday, burying his face in his hands at the end of the week-long duel against the Google-developed machine.
Despite his four-to-one defeat, the South Korean champion said that AlphaGo was "still at a level that can be challenged by humans."
"I am disappointed that the matches are over, and also disappointed that I could not end the series on a high note," he said at the pres conference, referring to his Sunday victory against the Go playing program.
"I think the humans still have a good chance," he added.
Dozens of millions of Go fans watched Lee's face off against the machine in the ancient Asian board game, where the players fight for territory by placing black or white stones on a 19-by-19 grid. The players were also competing for a $1 million to donate to charity.
Moving up in the ranks
"I'm kind of speechless, that was the most mind-blowing game experience so far," said Demis Hassabis, the CEO of Google's DeepMind company which developed the program.
"Early on ... it seemed that AlphaGo made quite a big mistake, but in the end it was able to get back into the match for an incredibly close, intense finish," Hassabis said. "We're just kind of stunned really."
Ahead of the Tuesday match, South Korea's Go Association said it was awarding an honorary grandmaster rank of "ninth dan" to AlphaGo, which is reserved for players whose skills in the board game border on "divinity."
Go Ratings website also ranked the AI as fourth best Go player in the world, one position above Lee Sedol.