Great Britain’s eventing team won gold after producing a dominant display in the showjumping finale at Tokyo Equestrian Park before Tom McEwen secured silver in the individual event.
And they comfortably retained top spot, with McEwen going clear on Toledo De Kerser, Collett having four faults aboard London 52 and Townend also collecting four with Ballaghmor Class.
It is Great Britain’s first Olympic team gold in eventing since Munich 1972, while Australia took silver and France bronze.
Final British rider Townend had the luxury of knowing he could knock four fences down and still win gold, such was the team’s dominance.
All three British riders were making Games debuts, but they delivered high-class displays to end a 49-year wait for team gold.
Britain finished on a score of 86.30, and it is a third equestrian medal in Tokyo for Team GB following Charlotte Dujardin, Carl Hester and Charlotte Fry winning dressage team bronze, and Dujardin also collecting an individual bronze.
It is only Britain’s third Olympic team crown in eventing after Stockholm in 1956 and Munich 16 years later.
And the success continued with McEwen taking silver in the individual competition on Toledo De Kerser after a faultless clear round.
Julia Krajewski took gold, but Townend had two fences down to finish fifth having begun the final showjumping round in second.
Collett, meanwhile, had eight faults when the final two fences in her round dropped, finishing ninth.
Reflecting on his team round, McEwen said: “He is a class horse and a great jumper, so it was just up to me on top.
“My nerves were fine. They (Townend and Collett) are both brilliant riders, and I had no doubt they would pull it straight out of the bag quite easily and comfortably.”
And Collett, who dropped places individually after having one fence down, added: “He (London 52) was his normal self at the start, then I think there was a reflection off the water and he just spooked, basically.
“He got it back together. It’s a shame, but it could have been a whole lot worse in that situation. It was a very clever course.”
Britain’s final winning margin was 13.9 penalties as their vintage collection of cross-country performances effectively turned the gold medal race into a procession.
Collett’s gold medal comes eight years after she was left in a coma for a week after falling on cross-country during an event in Hampshire.
It left her with a punctured lung, lacerated liver, a fractured shoulder and two broken ribs, while she also lost the sight in one eye.
She told the BBC: “Just to be here was more than a dream come true, and to be stood here, with a gold medal, I look back where I was eight years ago – I knew I was lucky to be alive, yet alone do the job I love.”
And Townend added: “I didn’t know how much we had in hand, so I put myself under a bit of pressure, but these guys made it very easy for me.
“It has not sunk in. We have got another round to jump, so we focus on that, but there will be a big celebration and I don’t think it will be with a cup of tea and a biscuit.
“Let’s hope we can inspire the next generation of kids. We are all from pretty normal backgrounds. It shows that hard work and dedication pays off.”