Witherspoon is producing the motion picture with Wicked's Marc Platt.
The biopic, according to the industry paper, will "explore the professional and personal life of [the] legendary performer, a singer, songwriter, composer and actress, [whose] career spanned nearly seven decades."
The jazz vocalist had hits with "Fever" and "Is That All There Is?" and also appeared in the films "The Jazz Singer" and "Pete Kelly's Blues." Her one Broadway outing was in the December 1983 Peg at the Lunt-Fontanne Theatre.
Ephron is currently represented Off-Broadway with Love, Loss, and What I Wore, which she co-wrote with her sister Delia.
Witherspoon won her Oscar for her performance in "Walk the Line."