The test was carried out on behalf of Team Lucky Strike Suzuki at Donington Park on 17 August and is believed to be the first positive doping case in the 500cc world championship.
Suzuki did not say what Gobert tested positive for and a spokeswoman declined to name the substance. She would not say whether it was a recreational or performance-enhancing drug.
"Team Lucky Strike Suzuki terminated its contract with Anthony Gobert following a positive drug test," said a Suzuki statement issued from Japan.
"Results made available to the team last week showed a positive reading for a prohibited substance. As a result, in the best interests of the team, the sport and fellow competitors, his contract was terminated with immediate effect."
There was no word on any replacement for Gobert in the three remaining races of the season and Suzuki are also expected to lose his team-mate, Darryl Beattie, next season when he returns to superbike racing.
Gobert, 22, was in his world championship debut season in the 500cc category, yet he thrived on controversy, clashing with the four-times world champion Michael Doohan before the season started, when he reportedly branded his compatriot a loser.
His best result of the season was seventh place in Austria, but he had scored points consistently and was 13th overall in the standings.
Gobert did not finish the British Grand Prix, retiring after just five laps and complaining of cramp in a hand. He had arrived at Donington late and lacking sleep, having missed his plane from Australia.Reuse content