Five machines were tested at the Royal Society in central London to see if they could fool people into thinking they were humans during text-based conversations.
The test was devised in 1950 by computer science pioneer and Second World War codebreaker Alan Turing, who said that if a machine was indistinguishable from a human, then it was "thinking".
No computer had ever previously passed the Turing Test, which requires 30% of human interrogators to be duped during a series of five-minute keyboard conversations, organisers from the University of Reading said.
But "Eugene Goostman", a computer programme developed to simulate a 13-year-old boy, managed to convince 33% of the judges that it was human, the university said.
Professor Kevin Warwick, from the University of Reading, said: "In the field of artificial intelligence there is no more iconic and controversial milestone than the Turing Test.
"It is fitting that such an important landmark has been reached at the Royal Society in London, the home of British science and the scene of many great advances in human understanding over the centuries. This milestone will go down in history as one of the most exciting."