Ashlee Simpson threw an engagement party!

Her party was "amazing".

In January it was said that she would be marrying musician-and-actor Evan Ross.

They've now had a pre-wedding celebration with their closest friends and family.

"What an amazing engagement party with all of our loved ones! We gettin' married :)" the star excitedly posted on Twitter.

She attached a selfie in a feathered headband gazing adoringly at Evan, who was wearing a white shirt and a furry coat.

Also in attendance was her older sister Jessica, 33, who is engaged to Eric Johnson.

"Celebrating my best friend and sister missbananahammock @ashleesimpson. I love her so much!" Jessica wrote on Instagram.

She also added a snap of herself with Ashlee, looking extremely slim in a cream mini dress with silver detail.

The blonde star has lost all the baby weight she put on while she was pregnant with her children with Eric, Maxwell and Ace.

Evan announced he was marrying Ashlee on his Twitter page earlier, in January.

The son of Diana Ross posted a picture of himself with his blonde fiancée gazing into the camera and showing off a sparkler on her ring finger.

"The love of my life said YES!!!" he captioned the photo.

It will be the second marriage for Ashlee, who married the star Pete Wentz in 2008.

They welcomed son Bronx the same year, but their divorce was finalised in 2011.

This is the first marriage for Evan.