Marc Marquez became the youngest rider to win a MotoGP race, after edging Honda team-mate and fellow Spaniard Dani Pedrosa to clinch the Grand Prix of the Americas title, in just his second race in the premier class.
The 20-year-old started the race on pole, after becoming the youngest rider to earn a MotoGP pole position in Saturday's qualifiers. Marquez, who is also the reigning Moto2 champion, was involved in a thrilling battle with Pedrosa throughout the race but held his nerve to take home the inaugural Grand Prix of the Americas title.
Pedrosa saw off a late challenge from compatriot, Yamaha rider and defending champion Jorge Lorenzo to finish second. Lorenzo took third, while Great Britain's Cal Crutchlow claimed fourth.
Marquez, 20 years and 63 days, now holds the record as the youngest rider to win a premier class Grand Prix, after taking over from legendary American rider Freddie Spencer, who was 20 years and 196 days when he won the 1982 Belgian GP.
"It is unbelievable. A first victory in MotoGP is a dream come true. I have to say thanks to all the people who helped me, especially the team because I could not do this without them," BBC quoted the youngster.
Marquez had finished third behind Lorenzo and nine-time world champion Valentino Rossi in the season-opener in Qatar two weeks ago.
The Texas triumph means Marquez now leads the world championship standings, level with Lorenzo on 41 points. His victory also marked the first time in the last 30 MotoGP races that a race has been won by a rider other than either Casey Stoner, Lorenzo or Pedrosa.
Earlier in the day, Spanish rider Nico Terol triumphed in Moto2, beating compatriot Esteve Rabat and Finland's Mika Kallio. Meanwhile, Spain's Alex Rins claimed the win in Moto3.
Grand Prix of the Americas results
1 Marc Marquez (SPA), Honda, 43:42.123
2 Dani Pedrosa (SPA), Honda, 43:43.657
3 Jorge Lorenzo (SPA), Yamaha, 43:45.504
4 Cal Crutchlow (GBR), Tech 3, 43:48.739
5 Stefan Bradl (GER), LCR, 43:54.797
6 Valentino Rossi (ITA), Yamaha, 43:58.738
7 Andrea Dovizioso (ITA), Ducati, 44:04.497
8 Alvaro Bautista (SPA), Gresini, 44:04.977
9 Nicky Hayden (USA), Ducati, 44:15.896
10 Andrea Iannone (ITA), Pramac, 44:24.235