LOS ANGELES — The intergalactic misfits of “Guardians of the Galaxy” are the summer’s box-office superheroes.

Marvel’s cosmic romp topped the Labor Day box office with a three-day take of $22 million — its third time in first place since its release five weeks ago, according to studio estimates Monday.

With North American ticket sales of more than $280 million so far, “Guardians” is also the summer’s — and the year’s — top-grossing film to date domestically.

Still, summer box-office totals are down almost 15 percent from last year, said Paul Dergarabedian, senior media analyst for box-office tracker Rentrak.

“This is the lowest summer since 2006 in terms of revenue,” he said.

“Before ‘Guardians,’ we were sitting on a 20 percent deficit compared to last year.”

1. “Guardians of the Galaxy,” $22.2 million ($19.7 million international).

2. “Teenage Mutant Ninja Turtles,” $15.7 million ($13 million international).

3. “If I Stay,” $11.6 million ($4.6 million international).

4. “Let’s Be Cops,” $10.5 million ($6.6 million international).

5. “As Above, So Below,” $10.3 million ($1.4 million international).

6. “The November Man,” $10.2 million.

7. “When the Game Stands Tall,” $8 million.

8. “The Giver,” $6.9 million.

9. “The Hundred-Foot Journey,” $6.3 million.

10. “The Expendables 3,” $4.5 million ($8.8 million international).