Billie Lourd gave birth to her first child and honored her late mother, Carrie Fisher, with the newborn's name.

On Thursday (September 24), the actress announced via Instagram that she gave birth to a son with fiancé, Austen Rydell. The news of the birth came as a big shock to fans as the 28-year-old American Horror Story star did not publicly announce her pregnancy prior to the birth announcement.

Lourd shared a photo of the baby's tiny feet and revealed his name: "Introducing: Kingston Fisher Lourd Rydell." His middle name, Fisher, honors the last name of her late mother.

See the sweet photo, below.

On Instagram, Lourd's Scream Queen co-stars shared their well wishes.

Lea Michele, who welcomed her first child in August, shared her excitement. "He’s finally here! So happy for you! Boy moms!" Michele wrote.

Emma Roberts, who is currently pregnant with her first child, also congratulated the couple. "Screaming!!! Love you guys so much," she wrote.

Mark Hamill, who starred in Star Wars films with both Lourd and Fisher, created a Twitter post for the newborn.

"Congratulations to #BillieLourd & #AustenRydell on the arrival of their firstborn child: Kingston Fisher Lourd Rydell!!!" he wrote. "I can't think of another baby with both 'KING' AND 'LORD' in their name. Nice."

See the sweet tribute, below.

Lourd and Rydell began dating in 2015 before briefly calling things off. They rekindled their romance in 2017.

In June, Rydell announced their engagement. "She said YES," he wrote. "(Actually she said “Duhhh”) But I guess that’s even better than yes?!?"