Golden couple Laura Trott and Jason Kenny - who will marry in September - won historic cycling golds as Britain made Rio 2016 their most successful overseas Olympics with 50 medals.
Trott became Britain's most successful female Olympian with her fourth gold, in the omnium.
Kenny equalled Sir Chris Hoy's record of six GB golds by winning the keirin.
There were further bronzes in cycling and boxing, with two more in gymnastics.
The nine medals won by Britain on day 11 is the most achieved on a single day in Rio so far and the team have won two more medals than at the same stage at London 2012, which was GB's most successful Games.
|Rio 2016 medal table|
|2. Great Britain||19||19||12||50|
|Full medal table|
Katy Marchant finished third in the women's track cycling sprint while Joshua Buatsi won boxing bronze in the light-heavyweight division.
Laugher, a gold medallist in the synchronised 3m springboard with Chris Mears, claimed his second Rio medal as he finished second in the individual event.
Victory for Kenny was GB's 19th gold of the 2016 Games.
Scott, 29, earlier sealed gold in sailing's Finn class to give Britain their fifth successive Olympic title in the event, and they are set for another sailing gold from Hannah Mills and Saskia Clark.
The run of success kept GB second in the medal table behind the United States, and above China, with five full days of action to come.
Britain racked up a total of 12 medals in the velodrome, with every member of the 10-strong track cycling team winning at least one.
Germany's Kristina Vogel, who beat James to gold in the women's sprint, wondered how GB's cyclists had managed to be so successful, saying: "It seems they do nothing for three years, then they start at the Olympics and kill us."
|Rio 2016 cycling medal table|
|1. Great Britain||6||4||2||12|
|3. United States||1||2||0||3|
|Full cycling medal table|
Joy for golden couple
Kenny, the 28-year-old from Bolton, won a dramatic keirin - the race was twice restarted because of infringements - to add to his team sprint and individual sprint victories.
Kenny and Trott, from Cheshunt, now boast 10 gold medals between them after both made British Olympic history in the velodrome.
Trott, 24, cried as Kenny pedalled his victory lap with his arms in the air, before the couple embraced and kissed as the crowd cheered.
Kenny said: "Today just felt like a dream. I'm just kind of so tired I'm just floating through it."
Hoy stood and applauded Kenny's achievement in matching his British record of six golds, calling it a "special moment" during his BBC analysis.
Trott, who had retained her omnium title in dominant fashion earlier in the evening, said: "I can't believe it - I did not expect that at all. I am just so happy that it all came together."
How the GB medal rush breaks down
- UK Sport's target of at least 48 medals passed with five days left
- Previous best at away Games - 47, Beijing 2008
- Best British Olympic medal haul away from home
- 15 sports have contributed to the medal tally so far
Team GB's Rio 2016 chef de mission Mark England said: "What this team has delivered so far at Rio 2016 is an incredible achievement and the country should be extremely proud of the athletes and their support staff."
More on the Team GB medal tracker can be found here.
IOC chief condemns 'shocking behaviour' as Lavillenie booed on podium
French pole vaulter Renaud Lavillenie was reduced to tears after being booed on the podium while he received his silver medal.
International Olympic Committee president Thomas Bach described the crowd's behaviour as "shocking" and "unacceptable at the Olympics".
Lavillenie had been booed by the crowd during Monday's competition, as he battled Brazilian Thiago Braz da Silva for gold, giving a thumbs-down gesture to the cameras as he prepared for an attempt.
After the medal ceremony, IAAF president Lord Coe, vice-president Sergey Bubka and Da Silva attempted to console Lavillenie, who simply wrote "no words" on Twitter.
Paula Radcliffe said: "That is just wrong. Ashamed of the track and field crowd tonight. Cheer your own as loud as you like but never disrespect the others."
Grabarz misses out on medal
In other events at the Olympic Stadium, Great Britain's 2012 bronze medallist Robbie Grabarz finished just outside the medals in the high jump as Canada's Derek Drouin won gold.
Grabarz, 28, went over 2.33m - although the bar fell down as he was celebrating and the clearance was only confirmed on appeal - but an earlier failure on his first attempt at 2.25m meant he finished joint fourth.
On the track, Eilidh Doyle qualified for the 400m hurdles final and Dina Asher-Smith made it through to the 200m final (02:30 BST on Thursday) as a fastest loser.
Anger at the boxing and swimming
Irish boxer Michael Conlan was furious with judges after losing a controversial points decision to Russia's Vladimir Nikitin in the quarter-finals.
"My dream has been shattered. It's been robbed. I came for gold and I've been cheated," said the amateur bantamweight world champion from Belfast.
British swimmer Jack Burnell, meanwhile, called his disqualification from the men's 10km open water swim "absolutely outrageous" after Dutchman Ferry Weertman took gold.
There was plenty of confusion after a dramatic finish, with Greece's Spiros Gianniotis initially given the win before being downgraded to silver.
Burnell's disqualification was for two yellow cards - he was unclear why the first was shown, while the second followed a tussle with a rival swimmer.
Other news from around the Games
Argentine sailor Santiago Lange, who lost part of a lung to cancer last year, teamed up with Cecilia Carranza Saroli to win gold in the Nacra 17 mixed class.
Jamaica's seven-time Olympic champion Usain Bolt ran 20.28 seconds to reach the semi-finals of the men's 200m (02:00 BST Thursday).
Bolt, who already has seven golds including the 100m in Rio, is seeking a "treble treble" of sprint titles, with the 4x100m relay to come.
Lightweight Robson Conceicao became Brazil's first Olympic boxing champion by beating France's Sofiane Oumiha.
Georgia's Lasha Talakhadze's won gold in the men's +105kg weightlifting category but riot police were called to the arena after judges ruled that Iranian favourite Behdad Salimikordasiabi had failed to register a total in the clean and jerk.
Fans booed as Salimikordasiabi and his coach angrily remonstrated with officials for several minutes before the contest was finished.
What's happening on day 12?
All times BST
- 10:00: Equestrian - Show Jumping individual competition - featuring Great Britain's Nick Skelton and Ben Maher
- 11:30: Golf - women's first round - Charley Hull and Catriona Matthew are GB's representatives
- 14:05-14:40: Athletics - Men's 5,000m heats - Mo Farah attempts to defend his title and win a second gold of Rio 2016
- 14:30: Badminton - Men's singles quarter-finals - featuring GB's Rajiv Ouseph
- 14:55: Athletics - Women's 800m heats - South Africa's Caster Semenya and GB's Lynsey Sharp in action
- 17:00: Football - Men's football semi-final - Brazil v Honduras
- 17:05: Sailing - Women's 470 - GB's Hannah Mills and Saskia Clark will win Olympic gold if they finish the medal race
- 21:00: Hockey - Women's semi-final - Great Britain v New Zealand
- 01:15 (Thursday): Athletics - Women's long jump final - Featuring Darya Klishina, the only Russian competing in athletics in Rio, plus GB's Lorraine Ugen and Jazmin Sawyers
- 02:00: Athletics - Men's 200m semi-finals - Usain Bolt, Justin Gatlin and GB's Adam Gemili, Danny Talbot and Nethaneel Mitchell-Blake in action
- 02:30: Athletics - Women's 200m final - GB's Dina Asher-Smith and world champion Dafne Schippers among those lining up
- 02:55: Athletics - Women's 100m hurdles final - (GB's Tiffany Porter and Cindy Ofili in semi-finals at 00:45)
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