Leo Max Frank (April 17, 1884 – August 17, 1915) was an American factory superintendent who was convicted in 1913 of the murder of a 13-year-old employee, Mary Phagan, in Atlanta, Georgia. His trial, conviction, and appeals attracted national attention. His lynching two years later, in response to the commutation of his death sentence, became the focus of social, regional, political, and racial concerns, particularly regarding antisemitism. Today, the consensus of researchers is that Frank was wrongly convicted and Jim Conley was likely the actual murderer.

Born to a Jewish-American family in Texas, Frank was raised in New York and earned a degree in mechanical engineering from Cornell University before moving to Atlanta in 1908. Marrying in 1910, he involved himself with the city's Jewish community and was elected president of the Atlanta chapter of the B'nai B'rith, a Jewish fraternal organization, in 1912. At that time, there were growing concerns regarding child labor at factories. One of these children was Mary Phagan, who worked at the National Pencil Company where Frank was director. The girl was strangled on April 26, 1913, and found dead in the factory's cellar the next morning. Two notes, made to look as if she had written them, were found beside her body. Based on the mention of a "night witch", they implicated the night watchman, Newt Lee. Over the course of their investigations, the police arrested several men, including Lee, Frank, and Jim Conley, a janitor at the factory.

On May 24, 1913, Frank was indicted on a charge of murder and the case opened at Fulton County Superior Court, July 28, 1913. The prosecution relied heavily on the testimony of Conley, who described himself as an accomplice in the aftermath of the murder, and who the defense at the trial argued was, in fact, the perpetrator of the murder. A guilty verdict was announced on August 25. Frank and his lawyers made a series of unsuccessful appeals; their final appeal to the Supreme Court of the United States failed in April 1915. Considering arguments from both sides as well as evidence not available at trial, Governor John M. Slaton commuted Frank's sentence from capital punishment to life imprisonment.

The case attracted national press attention and many reporters deemed the conviction a travesty. Within Georgia, this outside criticism fueled antisemitism and hatred toward Frank. On August 16, 1915, he was kidnapped from prison by a group of armed men, and lynched at Marietta, Mary Phagan's hometown, the next morning. The new governor vowed to punish the lynchers, who included prominent Marietta citizens, but nobody was charged. In 1986, Frank was posthumously pardoned by the Georgia State Board of Pardons and Paroles, although not officially absolved of the crime. The case has inspired books, movies, plays, and a TV miniseries.