One Is Guilty is a 1934 American pre-Code mystery crime film directed by Lambert Hillyer and starring Ralph Bellamy, Shirley Grey and Rita La Roy.

It is the second in a series of four films featuring Bellamy as Inspector Steve Trent following Before Midnight.

[1] Two further films, The Crime of Helen Stanley and Girl in Danger, were released later in the year.

[2] The body of a championboxer is found in an apartment complex.

Various suspects appear to have had the opportunity and the motive to kill the fighter.