"Britney and Sam are getting married today in a small ceremony at her home in Thousand Oaks," a source tells ET. "They are so excited. They have felt like true partners for a long time and can't wait to officially be husband and wife."
As for Spears' family, the source adds, "Britney's mom [Lynne Spears], dad [Jamie Spears], and [sister] Jamie Lynn were not invited. Ever since Britney and Sam talking about getting married and planning their wedding, inviting them was never a question."
As for what the bride will wear, the 40-year-old singer is expected to don a Versace gown at her wedding.
Preparation for the ceremony appears to be underway, with a giant white tent keeping much detail secure. However, a staircase leading into the tent can be seen.
On Wednesday, Spears documented an outing with Asghari where the two rode in the back of a Rolls Royce and sipped champagne. Spears posted videos of their adventure to her Instagram Stories on Wednesday evening, and showed off a fancy manicure as she held onto a tiny glass of bubbly.
In Spears' videos, she also strategically shows off the beautiful engagement ring Asghari designed for her. The model recently described her ring as "a princess cut, for a real life princess," during an interview with GQ last month.
In the same interview, Asghari kept mum on wedding details, but did call Spears his "soon-to-be wife."
Explaining what first attracted him to Spears when they met six years ago on the set of her "Slumber Party" music video, Asghari told GQ, "It was the humbleness that attracted me. She was very humble and she had a beautiful soul."
“Everything’s amazing,” Asghari told ET. “We’re so excited to start a new chapter, and everything’s so positive from here on out. “Everything is going to be new from here on out,” he added.
This will be Asghari's first marriage and Spears' third. She was briefly married to former friend Jason Alexander in 2004 and that same year, she wed Kevin Federline. Spears and Federline divorced in 2007 and share two sons, 16-year-old Sean Preston and 15-year-old Jayden.