The United States' Gabrielle Thomas blew away her rivals to win the women's 200m final at the Paris Olympics on Tuesday.

The 27-year-old showed blistering speed after the bend to finish in 21.83 seconds, 0.25 seconds ahead of Saint Lucia's Julien Alfred, who took silver after winning gold in the 100m.

Thomas' compatriot Brittany Brown claimed bronze, 0.12 seconds further back.

"I envisioned this from start to finish. I've been envisioning it since I made the team back in June," Thomas said. "I was not prepared for how I was going to feel when I crossed the line. There's no way to prepare yourself for that."

Thomas admitted she had been aided by the absence of two-time reigning 200m world champion Shericka Jackson, who withdrew from the 200m on Sunday due to a hamstring injury.

"I wouldn't say that I was relieved when Shericka pulled out," Thomas said. "I wish her all the best and it's hard that you can't have your reigning world champion competing but I was confident going into the race."

Alfred's silver gave Saint Lucia its second ever Olympic medal, three days after she secured the first.

The 23-year-old expressed hope that her performances would lift the profile of athletics in the Caribbean nation.

"The reaction has been really good," she said. "I'm really hoping what I did at my first Olympic Games can also inspire the youth in St Lucia and encourage the government to invest in the sport.

"I'm really hoping we can have many more athletes come on this stage and I hope what I did in the past five days can really inspire people back home to do better in the sport."