Pascal Le Segretain/Getty Images; Pascal Le Segretain/Getty Images
The Girls actress flashed her diamond sparkler for the first time at Sunday's Vanity Fair Oscar party. Williams, 25, looked pretty in pink wearing an Emilia Wickstead dress that featured an open back.
Williams and Van Veen began dating three years ago after meeting through mutual friends. And she's not the only Girls star who's in love: Lena Dunham is dating fun. Guitarist Jack Antonoff, while Zosia Mamet is with actor Evan Jonigkeit. Jemima Kirke, meanwhile, is married to lawyer Michael Mosberg.