City Lights

• Although not a boxing movie, per se, this 1931 semi-silent film comedy, starring Charlie Chaplin, features about a seven-minute boxing scene. Otherwise the plot concerns his "Tramp" character falling in love with a beautiful blind girl. Her family is in financial trouble. The Tramp's on-and-off friendship with a wealthy man allows him to be the girl's benefactor and suitor. (Internet Movie Database link.)
• Video of boxing scene