She's also known as Natasha Romanoff, a former agent of S.H.I.E.L.D. Her identity is publicly known. Born circa 1928, Natalia "Natasha" Romanova was apparently orphaned as a child when she was trapped in a burning building during an early attack on Stalingrad by enemy forces. Ivan Petrovitch Bezukhov, a Soviet soldier, found Natasha in the inferno and rescued her. Although Ivan kept a close eye on Natasha as she grew, by the late 1930s she had attracted the attention of Soviet intelligence, which began her training. In 1941, she was almost brainwashed into serving the ninja clan the Hand, but was saved by Ivan, Logan (James Howlett, later Wolverine) and Captain America.

Black Widow customarily wears two bracelets equipped to discharge the "widow's bite," high-frequency electrostatic bolts of up to 30,000 volts, capable of stunning even a superhuman opponent at a range of at least 20 feet, shoot tear gas cartridges and act as a radio transmitter. The bracelets' various functions are activated by galvanic sensors keyed to Black Widow's wrist musculature. At times she carries plastic explosive discs equivalent to 4 pounds of TNT in her belt and uses automatic weapons and/or combat knives as necessary.

Her costume is composed of a kevlar-like substance designed for maximum protective qualities, its fingers and feet lined with microscopic suction cups activated by an electrostatic charge, which allow her to adhere to any standard building material surface.