When fans hear Black Widow, they most likely think of Scarlett Johansson's character in the Black Widow, the character's first solo film which also marks the start of Phase 4. Here's how many Black Widows actually exist in the MCU.
Natasha Romanoff, whose real name is Natalia Romanova, was born in Russia where she was trained as a highly-skilled assassin from a young age. After graduating from the secret academy, known as the Red Room, Clint Barton was sent to kill her. Instead, he recruited her to leave her past behind and S.H.I.E.L.D. as a special agent. She did so and eventually found herself as a key member of the Avengers fighting alongside Clint, Captain America, Thor, Iron Man, the Hulk, and many others. During the Infinity War, Nat and Clint traveled to Vormir to retrieve the Soul Stone. Nat ended up sacrificing herself so the team could get their hands on the stone to assist in their efforts in taking down Thanos.
Black Widow is set after the events of Yelena Belova (Florence Pugh), a girl she trained with while in the Red Room. In addition, Nat will encounter Melina Vostokoff (Rachel Weisz), another trained assassin. Both women are considered Black Widows and they aren't the only ones besides Nat in the MCU to hold that name.
There Are Many Black Widows In The MCU
Students of the Red Room are brainwashed while also going through intense combat and weapons training. Upon graduating, the trainees are forcefully sterilized before being considered one of the world's deadliest assassins. These women are then considered Black Widows and when taking into the fact that the program has been in effect for decades before Nat came along, there are dozens upon dozens of other Black Widows out there. In fact, Agent Carter dove into the origins of the Black Widow Program in the 1940s, proving women have been transformed into Black Widows for over 50 years.
In the latest trailer for the Black Widow film, Nat states that there's a "new world of Widows." She turned her life around when she ed S.H.I.E.L.D. but she seems to fear that the Black Widows out there are nothing but trained killers. Nat feels like she's tried to do good so maybe fellow Black Widows could follow in her footsteps by straying away from Russian protocol to use their training for something bigger. With Natasha no longer alive for the primary MCU timeline, another Black Widow could potentially fill the void left by her death. It's also possible that the franchise will stop viewing Black Widow as an individual and consider the character a collective group.