The pair took to Instagram at the same time to share a photo of the spectacular ring, writing "I/She said yes."
The news promoted congratulations messages from celebrities such as Selena Gomez, Emily Ratajkowski, Demi Lovato and separate excited posts by both Nick and Kevin Jonas.
Sophie's Game of Thrones co-star and real-life BFF posted her own message, taking to Instagram to share the photo of Sophie's incredible ring: "Congratulations to my beautiful girlfriend on her engagement 💍"
"This is just one of MANY life milestones we'll share. Love you both 💗 #mophie #jophie #holymoly," Maisie wrote.
Emilia Clarke (Daenerys Targaryen), Lena Headey (Cersei Lannister), and Nathalie Emmanuel (Missandei) from Game of Thrones all liked Maisie's post.