A newsletter from Harbour's PR representatives list the actor as officially appearing alongside Scarlett Johansson and Florence Pugh in an undisclosed role in the Marvel Cinematic Universe film. It should be noted that Marvel Studios has not yet officially announced the film nor Harbour's casting at this time.
Harbour was first linked to the upcoming MCU film this past April shortly after the release of the Hellboy reboot in which he starred. Harbour subsequently expressed his interest in joining the film while remaining coy about the specifics, including his commitment.
Black Widow is currently in the middle of principal photography in Norway and Hungary and is expected to be released sometime next year. While set photos and video have leaked online, there has been sign of Harbour joining the production just yet.
Directed by Cate Shortland with a script by Ned Benson, Black Widow stars Scarlett Johansson, Florence Pugh and David Harbour. It is rumored to be released on May 1, 2020.