In the Marvel Cinematic Universe, Black Widow goes by "Natasha Romanoff"
Avengers -
(scene where Black Widow lures Banner out of the city to recruit him for the Avengers)
Bruce Banner : You brought me to the edge of the city, smart. I uh... assume the whole place is surrounded?
Natasha Romanoff : Just you and me.
Bruce Banner : And your actress buddy, is she a spy too? Do they start that young?
Natasha Romanoff : I did.
Bruce Banner : Who are you?
Natasha Romanoff : Natasha Romanoff.
Bruce Banner : Are you here to kill me, Miss Romanoff? Because that's not gonna work out for everyone.
Natasha Romonoff/Black Widow appears in the credit roll of Avengers; Avengers: Age Of Ultron; Captain America: The Winter Soldier; Captain America: Civil War
Natalie Rushman/Natasha Romonoff appears in the credit roll for Iron Man 2
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Actually, in comic books, in comic books, not the movies, in comic books, Black Widow was known as Natasha Romonoff until the early 1980's when somebody at Marvel noticed that Romonoff is the masculine of that last name and the correct femnine of that last name would be Romonova (which comic books started using from that point on).
In the movies she is credited as Natasha Romonoff/Black Widow and that is the name that should appear in description for the Black Widow moviestock.
Here is an article that might help you (link)