Both players were into their first Grand Slam singles final, but Barty showed no signs of nerves as she blasted through the first set for the loss of just one game.
Barty broke Vondrousova's serve again at the start of the second to take total control of the final and did not look back on her way to a dominant victory.
Vondrousova came into the final without having dropped a set to become the first teenage finalist at Roland-Garros since Ana Ivanovic in 2007.
Yet the Czech youngster looked nervy throughout the match, and a couple of errors and a double-fault helped Barty to break serve and take a 2-0 lead.
Barty looked full of confidence and secured a double break to move 4-0 up after only 13 minutes:
Vondrousova finally got a game on the scoreboard at 4-1, but she could not delay the inevitable as the relentless Barty cruised through the first set in under half an hour:
Barty attracted plenty of plaudits for her performance:
The second set followed in similar style. Barty broke Vondrousova at the start of the set and then managed to hold despite her opponent taking her to deuce:
Vondrousova showed some resistance to save two break points and hold for 2-1, but she failed to trouble the Australian on her serve.
The teenager had shown great determination to come from behind and beat Johanna Konta in her semi-final, but there was no repeat performance against Barty.
Indeed, the Australian kept her composure with victory in sight, breaking Vondrousova yet again at 5-3 and sealing victory with an overhead smash:
The 23-year-old could not hide her delight at her victory after the match, per freelance Ben Rothenberg:
The win also means Barty is the first Australian women to win the French Open since 1973, and she will rise up the world rankings:
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Ashleigh Barty wins her first career Grand Slam title at Roland Garros beating Marketa Vondrousova in straight sets. She's the first Australian woman to win the French Open since Margaret Court in 1973. Barty will reach a career-high No. 2 in the WTA Rankings on Monday. https://t.co/TVjlVkK4wj
It was a disappointing ending to an impressive French Open campaign from Vondrousova. She could not find her best tennis on Saturday but can take plenty of positives from her time in Paris.
Meanwhile, the win caps a memorable comeback for Barty after she quit the sport in 2014 to play professional cricket before announcing her return in 2016.