Hannah Mills became the most successful female Olympic sailor of all time as she grabbed 470 gold alongside Eilidh McIntyre.
The pair had a 14-point lead heading into the medal race, worth double points, and put in an assured performance to finish fifth.
It was more than enough for helm Mills to retain the title she won with Saskia Clark at Rio 2016, and for crew McIntyre to take gold on Olympic debut.
Mills, 33, from Cardiff, said: “It’s been one of the hardest weeks of my life. I’m sure for Eilidh as well, just every day, not being able to eat, just nerves building up, the emotion of just we’ve done it.
“It’s over. We’ve done what we came here to do and it’s amazing.
“Growing up, a lot of Olympians dreamed of being here one day and standing on top of the podium. And to do it twice with Saskia [Clark] before and Eilidh this time, I’ve had two incredible crews to sail with and I just feel incredibly lucky.
“The team around us here have been phenomenal. Big shout out to The National Lottery and everyone who plays the lottery because without you guys, we wouldn’t be here either.
“The support back home has been unreal so thank you everyone.”
The British pair finished with 38 points, a full 16 ahead of Poland in silver and France in bronze.
Top step was the crowning glory for a brilliant regatta for Team GB at Enoshima Bay, representing a third gold and fifth medal overall.
Mills and McIntyre’s triumph was Britain’s 30th gold medal in the sport and widened the lead at the top of the all-time medal table even further.
McIntyre, 27, from Hayling Island, said: “Fortunately nothing else [except gold] would have done for me and I think we’ve been so aligned on that for our entire campaign.
“To be honest I just couldn’t believe it. I can’t believe that this has happened. I’ve dreamt about it my entire life with my dad [Mike McIntyre, 1988 Olympic champion] and it’s just such an amazing feeling.
“I can wait to have it [the gold medal] around my neck.
“To my dad, thank you for everything. Thank you for being my inspiration, for being at the end of the phone whenever I wanted to talk.
“I want to thank my whole family and my poor mum… she’s had to live through the stress of this twice!”