“Fit to ride,” Honda tweeted, alongside a photo of the Spaniard giving the thumbs up riding pillion on a scooter after his medical at the Jerez circuit.
The six-time elite world champion was not expected to make his return until the Czech Grand Prix in August.
But the 27-year-old has defied medical odds to deny his rivals a chance to steal an early march in the coronavirus-shortened season’s title race.
Marquez returned to the scene of his crash in last Sunday’s opening Spanish Grand Prix from Barcelona where on Tuesday he had a titanium plate inserted into his right arm.
Also given the green light to race the second leg of the championship were two other crash victims from last weekend — LCR-Honda’s Cal Crutchlow, who required surgery on his left wrist, and Alex Rins.
Yamaha’s French rider Fabio Quartararo tops the nascent standings after taking his maiden MotoGP victory in the delayed curtainraiser last weekend.