Billie Lourd is engaged.

The 27-year-old actress - whose parents are Bryan Lourd and the late Carrie Fisher - is set to tie the knot with actor Austen Rydell after he popped the question.

Austen wrote on Instagram: ''She said YES!! (Actually she said 'Duhhh') But I guess that's even better than yes?!? (sic).''

Billie and Austen, 28, first started dating in 2016. They had one break-up but reunited in 2017 and have been together ever since.

For Valentine's Day this year, both Billie and Austen shared gushing posts about each other on Instagram.

He wrote: ''I found the best girl in the world. Happy Valentines Day to us!! We're hangin with the redwoods today,'' while Billie said: ''All 'round the world you make my world go 'round #toinfinityandbaeyond (sic).''

Following their split, Billie briefly dated 'Twilight' star Taylor Lautner, and he supported her after the tragic deaths of her mother Carrie and her grandmother Debbie Reynolds, who passed away just a day apart from each other.

And Carrie's brother Todd praised Taylor for supporting Billie.

He said: ''The truth of the matter is, the guy is pretty spectacular. He's a really deep person, and he has supported [Billie] amazingly. He's stepped up and acted like a husband would act. Not that that's what's going on, but it's just an amazing support system for her, and I'm glad he's in her life. That's not easy for me to say, if you think about it!

''As any uncle, you're suspicious of the guy hanging around your niece. She's cute and all that. She's had other boyfriends, good boyfriends, but I'm certainly going to give that guy the extra look-over. I don't give a sh*t what his background is.''