NEW YORK - Since 2008’s “Iron Man,” the Marvel machine has been one of the most unstoppable forces in box office history.

Now, though, that aura of invincibility is showing signs of wear and tear. The superhero factory hit a new low with the weekend launch of “The Marvels,” which opened with just $47 million, according to studio estimates Sunday.

The 33rd installment in the Marvel Cinematic Universe, a sequel to the 2019 Brie Larson-led “Captain Marvel,” managed less than a third of the $153.4 million its predecessor launched with before ultimately taking in $1.13 billion worldwide.

Sequels, especially in Marvel Land, aren’t supposed to fall off a cliff. Yet “The Marvels” debuted with more than $100 million less than “Captain Marvel” opened with — something no sequel before has ever done.

David A. Gross, who runs the movie consulting firm Franchise Research Entertainment, called it “an unprecedented Marvel box office collapse.”

The previous low for a Walt Disney Co.-owned Marvel movie was “Ant-Man,” which bowed with $57.2 million in 2015. Otherwise, you have to go outside the Disney MCU to find such a slow start for a Marvel movie — releases like Universal’s “The Incredible Hulk” with $55.4 million in 2008, Sony’s “Morbius” with $39 million in 2022 or 20th Century Fox’s “Fantastic Four” reboot with $25.6 million in 2015.

“The Marvels,” which added $63.3 million in overseas ticket sales, may go down as a turning point in the MCU. Over the years, the franchise has collected $33 billion globally — a point Disney noted in reporting its grosses Sunday.

But with movie screens and streaming platforms increasingly crowded with superhero films and series, some analysts have detected a new fatigue setting in for audiences. Disney chief executive Bob Iger himself has spoken about possible oversaturation for Marvel.

“Over the last three and a half years, the growth of the genre has stopped,” Mr. Gross wrote in a newsletter Sunday.

Either way, something is shifting for superheroes. The box office crown this year appears assured to go to “Barbie,” the year’s biggest smash with more than $1.4 billion worldwide for Warner Bros.

Marvel has still produced recent hits. “Guardians of the Galaxy Vol. 3” launched this summer with $118 million before raking in $845.6 million worldwide. Sony’s “Spider-Man: Across the Spider-Verse” earned $690.5 million globally and is widely expected to be an Oscar contender.

The actors strike also didn’t do “The Marvels” any favors.

The cast of the film weren’t permitted to promote the film until the strike was called off late Wednesday evening when SAG-AFTRA and the studios reached agreement. Ms. Larson and company quickly jumped onto social media and made surprise appearances in theaters.

Ms. Larson guested on “The Tonight Show” on Friday.

The normally orderly pattern of MCU releases has also been disrupted by the strikes.

After numerous strike-related delays, the only Marvel movie currently on the studio’s 2024 calendar is “Deadpool 3,” opening July 26.