The couple, who have been together since Day 5 in the villa, made their relationship official three weeks ago – and have even declared their love for each other.
They were battling to be crowned winners of the ITV2 show alongside Maura Higgins and Curtis Pritchard, Amber Gill and Greg O'Shea, and Ovie Soko and India Reynolds.
Tommy and Molly-Mae were odds-on favourites to win the fifth series with the bookmakers at 4/5.
Amber and Greg were second favourites at 11/8, India and Ovie were third at 5/1, while Maura and Curtis were the rank outsiders at 50/1.
Viewing figures are expected to be even higher than last year's final which saw an all-time ITV2 record of 3.6million viewers tuning in to watch Dani Dyer and Jack Fincham crowned winners.
It beat the 2017 final by almost one million, with the show enjoying an audience share of 19 per cent – more than six times the ITV2 average.
In last night's final episode all four couples attended the Love Island 2019 summer ball where they each offered their declarations of love.
Dressed in a tuxedo, boxer Tommy told Molly-Mae that he wants "my heart to speak to you, not my mouth" as he dropped the cards on which his speech was written on to the floor.
Speaking of their first meeting in the villa's private den, he said: "From the first moment I walked up into the Hideaway, I instantly knew I had seen the most beautiful girl on this entire planet. You're absolutely everything I've ever wanted in a girl."
In response, Molly-Mae, who wore a long, high-neck yellow dress said: "For someone whose career depends on fighting other people, you're the gentlest person I've ever met. You're my best friend and the most incredible dad to our Elly-Belly [her stuffed toy].
"Thank you for showing me kindness and nothing but pure love every day." The couple, who both live in Manchester, spoke about moving in together as they contemplated the next stage of their relationship on their final date last week.
Just after Tommy "coupled up" with Molly-Mae, he found himself at the centre of 486 Ofcom complaints when "predatory" Maura Higgins, 28, tried to get him to kiss her. She straddled him and continued to pursue the kiss, even after he politely refused.
The most watched episode of the series on July 3 was seen by more than six million and similar numbers are expected for the final.
The record-breaking episode showed the fallout between the group after the girls' return from Casa Amor – an alternative villa where they were given the opportunity to couple up with a new set of boys, while their counterparts stayed in the original villa and also met potential new partners.
Ratings body BARB said more than 4.7million watched the episode on TV, while 1.4million tuned in via phone, PC and tablet.
