An Unmarried Woman (Paul Mazursky, 1978)

 In the most acclaimed performance of her career, Jill Clayburgh stars as Erica, a woman who has it all - until her husband walks out and she is forced to reevaluate her life in Paul Mazursky's comic, touching, and poignant drama of single life in the '70's.
Also starring Michael Murphy, Cliff Gorman, and Alan Bates.