The Oscar-winning actress worked with director Rupert Goold on the film, in which she plays Garland circa 1968 as she performs a series of concerts at a legendary London nightclub.
In a statement to CNN, Goold added that the film will be about the price of “great performance” on an artist.
“For over 40 years Judy Garland had laughed and loved and entertained no matter what life threw at her, and her public adored her for it,” he said. “But she paid a price in a childhood lost to Hollywood, an emotional exhaustion and a yearning for a ‘normal’ life beyond the rainbow.”
He said he hopes the “powerful and moving story” will expose new audiences to Garland’s legacy.
Zellweger, who starred in the musical “Chicago,” lends her own singing voice to the film.
Goold said he didn’t want Zellweger to do an impersonation of the “Wizard of Oz” star but rather “make the songs her own.”
Tom Edge wrote the screenplay for the movie, which also stars Jessie Buckley, Finn Wittrock, and Rufus Sewell.