Flora Duffy of Bermuda claimed a historic first gold medal for her nation after taking control of the race – which started in wet and wild conditions – with a dominant run.
The 33-year-old, who rejected the chance to represent Britain as a teenager, finished one minute and 15 seconds ahead of Great Britain’s Georgia Taylor-Brown.
“It is an incredible, special moment. I crossed the line today but I did it for everyone in Bermuda,” said Duffy.
American Katie Zaferes, 32, won bronze as she finished more than a minute ahead of the rest of the field.
Vicky Holland, Britain’s third hopeful in the event, finished 13th after recovering from a crash on her bike.
As Duffy crossed the line, she blew kisses to those watching on, falling on her back beyond the tape and covering her eyes with her hands as she contemplated what she had achieved.
After winning the 2016 and 2017 world titles, followed by Commonwealth gold in 2018, Duffy spent more than a year battling a foot injury until the summer of 2019. And last winter her training was disrupted by a knee problem.
This victory was also significant for Bermuda, which became the least populous nation ever to win an Olympic gold.
“It was definitely a lot of emotion to deal with, it is slowly hitting me. This has been my dream since eight years old – I always wanted to be an Olympic champion,” Duffy told BBC Sport.
“There have been many tears, many heartbreaks, many times I wondered if I would ever be healthy again to compete at the top.”