The four-time podium finisher, who had been runner-up twice, finally scored his debut win after a dramatic race, which saw his two title rivals Dennis Hauger and Jack Doohan finish with no points after incidents in the last two laps.
Martins, who took his win at team MP Motorsport’s home race, started in fifth before making the most of his rapid pace and overtaking talent to claim the top spot on lap 16.
Fellow Frenchman Clement Novalak (Trident), who was in the lead until that point, finished second, while Frederik Vesti took third place for ART Grand Prix.
Martins’ teammate Caio Collet took fourth, with David Schumacher in fifth for Trident and Prema Racing’s Olli Caldwell in sixth.
Clement Novalak had taken the lead from Ido Cohen by Turn 1, leading the two-wide pack in a chaotic exit from the banking at Turn 3 before Johnathan Hoggard took a trip through the gravel.
Teammates Hauger and Caldwell were racing wheel-to-wheel on lap two, battling for fifth, with Hauger coming close to overtaking before backing off several times.
The safety car was deployed on lap three when Lorenzo Colombo suffered a left-rear puncture after contact with Hunter Yeany in Turn 1.
Racing resumed on lap six, with Iwasa plunging down the order after a lock-up at Turn 1 forced him to run wide and take to the escape road.
Martins took advantage of Vesti and Cohen’s battle for second to sweep up the inside of Turn 3 and take third position from the Dane.
Doohan and Schumacher made contact briefly as the pair chased Jak Crawford, who suffered a huge lock-up on the inside of Turn 1 on lap eight.
A DRS train had formed by lap nine, with Cohen closing in to within 0.7s of Novalak before falling back again. Martins attempted to pass the Carlin driver into Turn 1 but locked up as Iwasa had done several laps earlier.
By the halfway point, Vesti was right on the gearbox of Martins, while Novalak broke the one-second DRS window to Cohen, allowing him to build a 1.3s lead.
Martins eventually gained the momentum to pass Cohen with the help of DRS on the start-finish straight on lap 14, putting him up into second, just 0.7s behind Novalak.
Vesti also passed Cohen a lap later, taking the third podium spot in an almost carbon-copy of Martins’ earlier move.
The increasingly rapid Martins swept past compatriot Novalak for first on lap 16 despite the latter’s defensive moves, with the MP Motorsport car proving too quick to contend with.
Hauger finally overtook teammate Caldwell on the straight into lap 18, taking fifth place, before continuing his charge through the field and passing Cohen up into fourth place.
The safety car was deployed on lap 20 with just seven minutes to go after Amaury Cordeel’s Campos-run car became beached in the gravel at Turn 1, ending his race.
Racing resumed for lap 23, the penultimate tour, with Vesti almost letting Hauger through courtesy of a lock-up in the dusty line.
But a melee upon the restart saw Cohen make contact with Hauger into the banking, who suffered a right-rear puncture, plunging him down the order and out of the points.
The dramatic final lap also saw Schumacher pass Caldwell into P5, before Doohan went off the road and dropped down into 18th, leaving two of the three title contenders pointless for the race.