The National Basketball Association, alarmed by the death toll from shootings across the country, is stepping into the polarizing debate over guns, their regulation and the Second Amendment with an advertising campaign in partnership with one of the nation’s most aggressive advocates of stricter limits on firearm sales.

In a move with little precedent in professional sports, the N.B.A. is putting the weight of its multibillion-dollar brand and the prestige of its star athletes behind a series of television commercials calling for an end to gun violence.

The first ads, timed to reach millions of basketball fans during a series of marquee games on Christmas Day, focus on shooting victims and contain no policy recommendations. The words “gun control” are never mentioned.

But the organization that paid for the ads, Everytown for Gun Safety, has a robust and controversial agenda: It was founded by Michael R. Bloomberg, a former New York mayor, specifically as a counterweight to the National Rifle Association and battles at the local, state and federal level to expand background checks for gun buyers, strengthen penalties for gun trafficking and ban gun sales to people convicted of domestic abuse.