The singer reached the impressive milestone this month, after shifting five million units of albums Loud and Talk That Talk in the last 12 months.
"Selling 15 million records in the UK is a remarkable achievement," Mercury Music Group president Jason Iley told Music Week.
"Rihanna's only 24 and I have no doubt she'll sell another 15 million records in the near future. It's not about speed, it's about longevity, and Rihanna has a long career ahead of her."
Rihanna released her debut album Music of the Sun in the UK seven years ago, and five of her six subsequent records have achieved multi-platinum status.
The star is credited as the only female artist to have had a number one single in five consecutive years in the UK, and to date has totalled six chart-topping singles and three number one albums.
"Her work ethic is incredible. She understands the label, as well as the promotional opportunities that we've created."
Rihanna recently insisted that she will release a collaboration with friend Katy Perry, adding: "We are still trying to make a song together."