The singer captioned an Instagram post in which she shared the news, "I can’t f****** believe it!!!!!!"
In a video accompanying the post, Asghari can be heard asking, "You like it?"
"Yes!" Spears gushes as she flashes her ring at the camera.
"The couple made their long-standing relationship official today and are deeply touched by the support, dedication and love expressed to them," Asghari’s talent manager Brandon Cohen reportedly told Page Six of the engagement. "Roman Malayev from NYC is the ring designer. He couldn’t be more happier [sic] to be involved and make this a one-of-a-kind ring."
The outlet notes that the 4-karat diamond ring has the word "Lioness," Asghari's nickname for Spears, engraved inside the band.
The engagement marks yet another victory for Spears, who in recent months has been publicly fighting her conservatorship, which has been in place since 2009.
During a bombshell court testimony in June, Spears shared that she wasn't allowed to get married or have more kids under the terms of her conservatorship.
Spears' father, Jamie Spears, filed to end the court-appointed arrangement on Tuesday, paving the way for Spears and Asghari to move forward with their relationship.
Spears' conservatorship remains in place for the time being, with the next hearing scheduled for Sept. 29.