Adore You, performed and written by Styles with Amy Allen, Tyler Johnson and Kid Harpoon, was named winner of most performed work of 2020 at the ceremony in London.
Composer Blanck Mass also won his first Ivor for best original film score for Bafta-nominated Irish crime drama Calm With Horses, directed by Nick Rowland in his feature debut.
This year 70% of the 26 songwriters and composers recognised with an Ivor were first-time awardees.
Indie-soul singer-songwriter Lianne La Havas' self-titled third album won the award for best album.
Written with Matthew Hales, the record depicts the stages of a relationship from early romance to its end.
This is their first win at the Ivor Novello Awards having both been first been nominated in 2013 for La Havas’ debut album, Is Your Love Big Enough?
Celeste and her songwriting partner Jamie Hartman took home the Ivor for songwriter of the year for their work on tracks such as Stop this Flame and A Little Love for the John Lewis Christmas advert.
The rising star award with Apple Music, now in its second year, went to 20-year-old Willow Kayne, whose music combines punk, hip hop and electronica and whose aesthetic approach draws inspiration from fashion and graphic design.
Kayne was paired with Chic star Nile Rodgers as part of a mentorship scheme organised by the body.
He said: "Willow has a fresh and exciting sound and the energy and determination to match it. She’s a genuine star in the making and I can’t wait to support her on her musical journey."
Jon Bon Jovi and his former guitarist Richie Sambora collected the special international award for a musical partnership spanning 30 years.
Best contemporary song went to Children Of The Internet by rapper Dave and producer Fraser T Smith.
Performed under Smith’s Future Utopia moniker, featuring Dave and Es Devlin, the track highlighted the impact of social media and hyper-connectivity on the younger generations.
Among the other winners were Obongjayar and Barney Lister in their first Ivor win for God’s Own Children, which took home best song musically and lyrically, and Alison Goldfrapp and Will Gregory were recognised with the inspiration gong for their work as electronic music duo Goldfrapp.
Shaznay Lewis, Ivor Novello Award winner and chair of The Ivors Awards Committee at The Ivors Academy, said: "I’m amazed by the impressive range of talent who have joined the UK’s roll call of songwriting greats by winning an Ivor Novello Award.
"Each one brings joy to so many and creates the soundtrack to our lives. As well as being astounded by their achievements, I would like to thank every winner and nominee for creating the most wonderful and era-defining music."
Source: Press Association