The song “Happy Birthday to You” is widely credited for being the most performed song in the world. But one of its latest venues may be the federal courthouse in Manhattan, where the only parties may be the litigants to a new legal battle.

The dispute stems from a lawsuit filed on Thursday by a filmmaker in New York who is seeking to have the court declare the popular ditty to be in the public domain, and to block a music company from claiming it owns the copyright to the song and charging licensing fees for its use.

The filmmaker, Jennifer Nelson, was producing a documentary movie, tentatively titled “Happy Birthday,” about the song, the lawsuit said. In one proposed scene, the song was to be performed.

But to use it in the film, she was told she would have to pay $1,500 and enter into a licensing agreement with Warner/Chappell, the publishing arm of the Warner Music Group. Ms. Nelson’s company, Good Morning to You Productions, paid the fee and entered into the agreement, the suit says.

“Before I began my filmmaking career,” Ms. Nelson said in an e-mail forwarded by her lawyer, “I never thought the song was owned by anyone. I thought it belonged to everyone.”

The lawsuit notes that in the late 1800s, two sisters, Mildred J. Hill and Patty Smith Hill, wrote a song with the same melody called “Good Morning to All.” The suit tracks that song’s evolution into the familiar birthday song, and its ownership over more than a century.

But although Warner/Chappell claims ownership of “Happy Birthday to You,” the song was “just a public adaptation” of the original song, one of Ms. Nelson’s lawyers, Mark C. Rifkin, said in a phone interview.

“It’s a song created by the public, it belongs to the public, and it needs to go back to the public,” Mr. Rifkin said.