Honda rider Marquez, whose Americas wins have all come from the pole, won in 43min 58.770sec with Yamaha rider Rossi second in his best-ever finish at the Texas track.
Spanish Honda rider Dani Pedrosa was third in his third podium finish over the 5.513km, 20-turn layout in Austin.
Marquez rebounded from an early crash out two weeks ago at Argentina as he tries to jump start his bid for a fourth world championship in five years and second in a row.
Spaniard Maverick Vinales went out on his Yamaha after 20 of 21 laps and lost his overall season points lead to teammate Rossi, who stands on 56 to 50 for Vinales and Marquez jumping to third overall on 38.
Off the line it was an absolutely stunning swoop around the outside for Pedrosa from the second row to lead as the Spaniard overtook teammate and polesitter Marquez to lead through Turn 1, with Rossi tucked in behind the two Repsol Honda machines.
Ducati’s Jorge Lorenzo got a great launch from sixth position to overtake Viñales, and the two men duelled it out until Johann Zarco of Monster Yamaha Tech 3 got into the action and followed Viñales past the Mallorcan – before the drama struck.
After two wins from two in the first races of the season, Viñales suddenly slid out of contention at Turn 18 – lowsiding safely, but out of the fight for victory and taking home a 0 for the first time since Argentina 2016.
Morbidelli wins third Moto2 race in a row
Earlier, Italy’s Franco Morbidelli captured his third consecutive Moto2 victory to pad his points lead.
The pole-sitter won in 41mins 20.078secs, defeating Swiss rider Thomas Luthi by 2.633 seconds with Japan’s Takaaki Nakagami third, 6.809 seconds adrift, to complete a Kalex rider podium sweep.
Fenati defends Moto3 title in Americas GP
Italy’s Romano Fenati won his second consecutive Moto3 Americas title, defeating Spain’s Jorge Martin by 4.504 seconds yesterday.
Fenati, who started on the outside of row one, crossed the line in 27mins, 15.841secs on the way to victory with Martin second and Italy’s Fabio Di Giannantonio third, 0.03 behind Martin, to complete a Honda podium sweep.
RESULTS and standings
MotoGP results (top 10)
1. Marc Marquez (Honda) 43:58.770
2. Valentino Rossi (Yamaha) 44:01.839
3. Dani Pedrosa (Honda) 44:03.882
4. Cal Crutchlow (Honda) 44:06.408
5. Johann Zarco (Yamaha) 44:06.727
6. Andrea Dovizioso (Ducati) 44:12.828
7. Andrea Iannone (Suzuki) 44:14.261
8. Danilo Petrucci (Ducati) 44:15.542
9. Jorge Lorenzo (Ducati) 44:16.749
10. Jack Miller (Honda) 44:17.26
MotoGP standings (top 10)
1. Valentino Rossi (Yamaha) 56
2. Maverick Vinales (Yamaha) 50
3. Marc Marquez (Honda) 38
4. Andrea Dovizioso (Ducati) 30
5. Cal Crutchlow (Honda) 29
6. Dani Pedrosa (Honda) 27
7. Johann Zarco (Yamaha) 22
8. Jonas Folger (Yamaha Tech3) 21
9. Scott Redding (Ducati) 21
10. Jonas Folger (Yamaha Tech3) 21
Moto2 results (top five)
1. Franco Morbidelli (Kalex) 41:20.078
2. Thomas Luethi (Kalex) 41:22.711
3. Takaaki Nakagami (Kalex) 41:26.887
4. Alex Marquez (Kalex) 41:29.930
5. Dominique Aegerter (Suter) 41:31.005
Moto2 standings (top five)
1. Franco Morbidelli (Kalex) 75
2. Thomas Luethi (Kalex) 56
3. Miguel Oliveira (KTM) 43
4. Takaaki Nakagami (Kalex) 32
5. Xavi Vierge (Tech 3) 25
Moto3 results (top five)
1. Romano Fenati (Honda) 27:15.841
2. Jorge Martin (Honda) 27:20.345
3. Fabio Di Giannantonio (Honda) 27:20.368
4. Enea Bastianini (Honda) 27:20.514
5. Nicolo Bulega (KTM) 27:20.809
Moto3 standings (top five)
1. Joan Mir (Honda) 58
2. Jorge Martin (Honda) 52
3. John McPhee (Honda) 49
4. Romano Fenati (Honda) 45
5. Andrea Migno (KTM) 25
