The pop star announced the engagement with a video posted to Instagram in which she showed off a large diamond sparkler.
Asghari’s manager Brandon Cohen shared in a statement to PEOPLE that he is “proud to celebrate and confirm the engagement”.
“The couple made their long-standing relationship official today and are deeply touched by the support, dedication and love expressed to them,” said Cohen.
The stunning ring was designed by Roman Malayev, with Cohen saying the New York jeweller “couldn’t be happier to be involved and make this one-of-a-kind ring”.
It’s believed Asghari’s nickname for Spears, ‘Lioness’, is engraved inside the band.
Spears, 39, and Asghari, 27, first met in 2016 on the set of the singer’s ‘Slumber Party’ music video.