During an interview promoting the highly anticipated action sequel, in which they play Hawkeye and Captain America, respectively, a reporter with Digital Spy asked the actors about Black Widow's romantic prospects with their characters.
To that, Renner, 44, replied: "She's a slut."
Evans, 33, let out a hearty laugh and agreed.
"I was going to say something along that line," he said. "A complete whore ... she's just flirting with everybody, leading everybody on."
Then Renner piled on, saying that "she has a prosthetic leg anyway."
Fans of the films and others decried the costars' remarks about the sole female Avenger going into "Age of Ultron," saying on Twitter that the men were slut-shaming the character and accusing them of sexism and misogyny.
Incidentally, Black Widow, a.k.a. Natasha Romanov, takes a romantic turn with Mark Ruffalo's Bruce Banner, a.k.a. the Hulk, in the latest film.
On Friday, the "Avengers" stars put out separate statements apologizing for the barbs.
"I am sorry that this tasteless joke about a fictional character offended anyone," Renner said in a statement to the Los Angeles Times. "It was not meant to be serious in any way. Just poking fun during an exhausting and tedious press tour."
"Yesterday we were asked about the rumors that Black Widow wanted to be in a relationship with both Hawkeye and Captain America," Evans said in a separate statement to The Times. "We answered in a juvenile and offensive way that rightfully angered some fans. I regret it and sincerely apologize."
The actors have been making the rounds since April 13 to bolster the big-budget Marvel film ahead of its May 1 release. The promo tour also got to costar Robert Downey Jr., who walked out during an interview with a British TV reporter when he was asked about his history with drugs, substance abuse, prison and his father.
"You seem OK, it's just getting a little Diane Sawyer-esque," Downey told Krishnan Guru-Murthy after the line of questioning got personal.
Reps for Johansson and Marvel did not immediately respond to The Times' requests for comment.
Times staff writers Noelene Clark and Tracy Brown contributed to this report.
Follow me on Twitter @NardineSaad.