Reese Witherspoon and Fox 2000 are mounting an untitled biopic of singer Peggy Lee starring Witherspoon, with Nora Ephron writing and attached to direct.Witherspoon — the driving force behind the project — is producing with Marc Platt. Fox and Witherspoon’s reps are still hammering out the details of her deal to topline. Witherspoon secured the rights to Lee’s story from the late singer’s estate after meeting with Lee’s granddaughter, Holly Foster-Wells. Witherspoon then went to Platt, with whom she teamed on the “Legally Blonde” franchise. In addition to film and TV, Platt has produced Broadway shows, including the musical smash “Wicked.” Witherspoon next approached Ephron, who turned out to be a longtime fan of Lee’s. Elizabeth Gabler’s Fox 2000 was a natural home for the project, having produced “Walk the Line,” the Johnny Cash biopic toplining Joaquin Phoenix and Witherspoon. Fox 2000 and Witherspoon are also working together on “Water for Elephants,” which just wrapped shooting and toplines Witherspoon, Christoph Waltz and Robert Pattinson. Like “Walk the Line,” the Lee biopic will explore the professional and personal life of a legendary performer. A singer, songwriter, composer and actress, Lee’s career spanned nearly seven decades. Lee rose to prominence during the big band era. Her first hit was “Why Don’t You Do Right?” with Benny Goodman, recorded in 1942. She recorded a series of hit albums and songs, including “Fever” and “Is That All There Is?” during the next 30 years. She’s regarded as one of the most influential jazz vocalists of all time. Lee also was a prolific songwriter. She penned a number of songs and voiced several characters in Disney’s 1955 animated hit “Lady in the Tramp.” In the early 1990s, Lee won a landmark case against the Mouse House for royalties from homevid sales of the pic. Her career extended to television and the bigscreen, where her credits included the 1952 redo of “The Jazz Singer” and “Pete Kelly’s Blues.” Ephron last directed Sony’s “Julie & Julia” from her adapted script. Witherspoon is next in theaters in December in comedy “How Do You Know?” opposite Paul Rudd and Owen Wilson. “Water for Elephants” is set for release in April. Witherspoon is repped by CAA and Management 360; Ephron is repped by CAA.