Annabelle Wallis and Sebastian Stan are expecting their first child together … and the actress just debuted her new baby bump in NYC!

Check out the pic … the “Peaky Blinders” star wore a striped denim button-down, slacks and white sneakers while taking her 2 dogs on a walk through the city Monday.

As you know … Sebastian and Annabelle have been together for about four years, and TMZ broke the story about the pregnancy last month.

The timing came during a particularly busy stretch for both stars … Sebastian has a packed year ahead with the upcoming release of his film “Fjord” … along with the highly anticipated Marvel installment “Avengers: Doomsday.”