The Global-owned network – which counts former Spice Girl Emma Bunton, as well as Toby Anstis and Jenni Falconer among its presenters – has leapfrogged over its nearest rival, the sister network Capital, in the latest Rajar figures.
With listeners up by a quarter on its previous audience of 7.3 million to the end of December 2013, Heart has been given a boost by its London breakfast duo of Emma Bunton and Jamie Theakston, who attracted 779,000 weekly listeners.
Each of the Heart network's 9.1 million listeners tuned in for an average seven hours each week.
Capital, which had spent three quarters as the biggest commercial brand, reported a weekly reach of 7.3 million in the first quarter of 2014, down 2.4 per cent from the final quarter of 2013, but an increase of 5.6 per cent year on year.
Classic FM pulled in 5.3 million listeners, down five per cent year on year, while Bauer's Kiss UK had a weekly reach of 4.6 million, up an impressive 12 per cent year on year.
In Absolute Radio's first quarter as a Bauer Media-owned station its network reached an average of 3.5 million listeners, an increase of 8.9 per cent year on year but flat on the period (-0.1 per cent).
Nationally, listening to the radio on mobile phone and tablet is burgeoning, with 18 per cent of adults claiming to listen via their devices at least once a month – an upsurge of 43 per cent year on year.
Of these, 32 per cent of 15- to 24-year-olds say they listen to the radio on their phone or tablet at least once a month.