SEOUL, South Korea — Computer, one. Human, zero.

A Google computer program stunned one of the world’s top players on Wednesday in a round of Go, which is believed to be the most complex board game ever created.

The match — between Google DeepMind’s AlphaGo and the South Korean Go master Lee Se-dol — was viewed as an important test of how far research into artificial intelligence has come in its quest to create machines smarter than humans.

“I am very surprised because I have never thought I would lose,” Mr. Lee said at a news conference in Seoul. “I didn’t know that AlphaGo would play such a perfect Go.”

Mr. Lee acknowledged defeat after three and a half hours of play.

Demis Hassabis, the founder and chief executive of Google’s artificial intelligence team DeepMind, the creator of AlphaGo, called the program’s victory a “historic moment.”