Mourning Becomes Electra is a 1947 American drama film by Dudley Nichols adapted from the 1931 Eugene O'Neill play Mourning Becomes Electra, based in turn on the Oresteia. The film stars Rosalind Russell, Michael Redgrave, Raymond Massey, Katina Paxinou, Leo Genn and Kirk Douglas.

Rosalind Russell was nominated for the Best Actress in a Leading Role and Michael Redgrave was nominated for the Best Actor in a Leading Role. Originally released by RKO Radio Pictures at nearly three hours running time, it was eventually cut to 105 minutes (losing more than an hour) after it performed poorly at the box-office and won no Oscars. Though the complete version appears to be lost, the British cut, running 159 minutes, survives and is available on DVD and has been shown on Turner Classic Movies.

A major Oscar upset occurred in connection with the film. All who saw it had taken it for granted that Rosalind Russell would win for her performance as Lavinia, to the point that Russell actually began to rise from her seat just before the winner's name was called. However, it was Loretta Young, and not Russell, who was named Best Actress, for her performance in The Farmer's Daughter.

The film recorded a loss of $2,310,000, making it one of RKO's biggest financial failures.