The Americans costars welcomed their first child together in May
Keri Russell pregnant Matthew Rhys

Keri Russell has finally lifted the veil on her newborn baby!

On Friday, the actress revealed the name and sex of her first child with her The Americans costar Matthew Rhys: The couple welcomed a son, whom they named Sam.

Russell broke the news during an appearance on the Today show Friday after host Matt Lauer teasingly addressed the fact that the star had kept things very hush-hush and had not yet officially announced her third child’s arrival.

“I mean, I guess not,” Russell said with a laugh. “Where do you reveal that?”

“You could do it right now!” Lauer suggested.

“We had a boy,” Russell said. “[His name is] Sam. He’s so good. He’s big and fat and nice.”

Russell also said Rhys, a new father, is doing “so well.”

WATCH: Keri Russell Reveals Name and Sex of Her First Child with Matthew Rhys – and Says the Baby Is Doing ‘So Good’

Russell, 40, and Rhys, 41, welcomed their son in May. Sam is Rhys’ first child and the third for Russell, who is already mom to daughter Willa, 4, and son River, 9, with ex-husband Shane Deary.

The Americans stars — who play Russian spies posing as a suburban American couple on the hit FX spy drama — have largely kept their relationship under wraps though after months of speculation, PEOPLE confirmed in April 2014 that the two were dating.

Aurelie Corinthios