More than 3.6 million people tuned in to watch Amber Gill and Greg O’Shea be named the surprise winners of Love Island, according to ITV.
A further 400,000 fans streamed the episode on non-TV devices such as phones and tablets.
The climax of the ITV2 dating series was watched by 3.63 million, up slightly from the 3.56 million who tuned in to watch Dani Dyer and Jack Fincham win last year.
This made it the most watched Love Island final ever and the most watched episode of the series, which has been a ratings triumph for the youth-skewing channel.
Amber and Greg were the surprise winners of the 2019 series, beating favourites Molly-Mae Hague and Tommy Fury in a shock twist.
They are the first winning pair who have not been together for the majority of the series.
Greg only entered the villa in the July 16 episode as the very last bombshell of the two-month series.
He said: “I never thought this was going to happen at any stage.
“I wasn’t even in the villa two weeks ago, I wasn’t here two weeks ago and obviously the public saw us kick it off and it just went from there.”
Amber said: “It’s amazing, I have no words.”
Romance blossomed between the pair after Amber was dumped by Michael Griffiths for Joanna Chimonides.
After Joanna was axed, Michael expressed interest in reviving his romance with Amber but Amber instead chose to pursue a relationship with the newcomer.
The pair now stand to rake in a lucrative income in endorsements and appearances, but will be subjected to increased scrutiny and attention.
Amber already has 1.8 million followers on Instagram, while Greg has 587,000.
They won the first series since ITV announced an enhanced duty of care process for participants on the show, including a minimum of eight therapy sessions.
The deaths of former Love Island contestants Sophie Gradon and Mike Thalassitis led to increased scrutiny on ITV over the reality show’s aftercare.
On Monday, Ofcom announced proposals for new rules to ensure people who take part in television and radio shows are properly looked after by broadcasters.
One element of the proposed guidance for post-production is advising potential participants on steps to minimise or limit social media contact post-transmission.
The Digital, Culture, Media and Sport Committee has also launched an inquiry into reality TV following the deaths of Gradon, Thalassitis, and The Jeremy Kyle Show participant Steve Dymond.
After the winners of the series were announced, runners up Molly-Mae and Tommy said they were thrilled for Amber and Greg.
“Amber has had a hard time in here, she deserves everything that’s coming to her,” said boxer Tommy.
As well as the title, the winning couple were given a cheque for £50,000.
The final also saw Ovie Soko and India Reynolds come third, and Curtis Pritchard and Maura Higgins come fourth.
During the final episode, the contestants made declarations of love to each other as they attended a romantic summer ball.
Greg penned a poem for Amber, in which he said he loved that she was “unique”.
Amber, who had a tough time earlier in the series when she was ditched by Michael, replied that Greg had changed her experience at the 11th hour.
“You picked me up when I was at my most vulnerable and helped me to rediscover my smile,” she said.
The series has been a huge hit, with millions of people tuning in for the couplings, dumpings and drama. It was viewed by more than six million people at its peak this year.
It has been announced that next year the show will run for two series.