The actress, 39, was spotted wearing her engagement ring while arriving to JFK Airport in New York City early Friday morning.
Although it is difficult to tell, the ring appears to be a dainty silver minimalistic band that features a large pearl.
Williams paired the elegant piece with a navy blazer — which covered her growing baby bump — and light wash jeans with white boots.
A source confirmed to PEOPLE this week that Williams is engaged to Kail and that the two are also expecting their first child together. Williams’ daughter Matilda, 14, played matchmaker, the source said.
The actress and Kail, 42, were photographed together in London where she is busy filming Venom 2. Williams was spotted buying baby clothes at Seraphine’s maternity boutique in Kensington.
A rep for the actress has not commented.
The actress shared Matilda with the late actor Heath Ledger.
Kail directed Williams in the drama Fosse/Verdon, for which she won the Emmy Award for lead actress. The director is close friends with Lin-Manuel Miranda and directed his musical In the Heights on Broadway. He also won an Emmy for directing Grease: Live.
Williams’ new romance comes more than a year after she married indie musician Phil Elverum during the summer of 2018. The two quietly separated in early 2019, but Williams told Vanity Fair shortly after they married that their relationship provided the “radical acceptance” she had been searching for since her romance with ex-boyfriend Ledger.
Williams has been candid in the past about finding love after Ledger’s death in 2008.
“I never gave up on love,” she told Vanity Fair in 2018 about moving on. “I always say to Matilda, ‘Your dad loved me before anybody thought I was talented, or pretty, or had nice clothes.’”