Turner and Jonas shared the same photo on Instagram on Sunday of her hand sporting a diamond ring and resting on top of his. Turner noted in her caption that she "said yes."
The 21-year-old Turner has starred as Sansa Stark on "Game of Thrones" since she was 15. She played Jean Gray in last year's "X-Men: Apocalypse" and will reprise the role in a follow-up next year.
Jonas shot to fame with his siblings as part of The Jonas Brothers. The 28-year-old now fronts the pop band DNCE.