Nathan Freudenthal Leopold, Jr. (November 19, 1904 – August 29, 1971)[1] and Richard Albert Loeb (/ˈloʊb/; June 11, 1905 – January 28, 1936), usually referred to collectively as Leopold and Loeb, were two wealthy students at the University of Chicago who in May 1924 kidnapped and murdered 14-year-old Robert Franks in Chicago. They committed the murder—widely characterized at the time as "the crime of the century"—as a demonstration of their perceived intellectual superiority, which, they thought, rendered them capable of carrying out a "perfect crime", and absolved them of responsibility for their actions.

After the two men were arrested, Loeb's parents retained Clarence Darrow as counsel for their defense. Darrow's 12-hour-long summation at their sentencing hearing is noted for its influential criticism of capital punishment as retributive rather than transformative justice. Both men were sentenced to life imprisonment plus 99 years. Loeb was killed by a fellow prisoner in 1936; Leopold was released on parole in 1958.

The two young men grew up with their respective families in the affluent Kenwood neighborhood on Chicago's South Side. The Loebs owned a summer estate, Castle Farms, in Charlevoix, Michigan, in addition to their mansion in Kenwood, two blocks from the Leopold home.

Though Leopold and Loeb knew each other casually while growing up, their relationship flourished at the University of Chicago, particularly after they discovered a mutual interest in crime. Leopold was particularly fascinated by Friedrich Nietzsche's concept of supermen (Übermenschen)—transcendent individuals, possessing extraordinary and unusual capabilities, whose superior intellects allowed them to rise above the laws and rules that bound the unimportant, average populace. Leopold believed that he was one of these individuals, and as such, by his interpretation of Nietzsche's doctrines, he was not bound by any of society's normal ethics or rules.[6] Before long he had convinced Loeb that he, too, was an Übermensch. In a letter to Loeb, Leopold wrote, "A superman ... is, on account of certain superior qualities inherent in him, exempted from the ordinary laws which govern men. He is not liable for anything he may do."

The pair began asserting their perceived immunity from normal restrictions with acts of petty theft and vandalism. Breaking into a fraternity house at the university, they stole penknives, a camera, and a typewriter that they later used to type their ransom note. Emboldened, they progressed to a series of more serious crimes, including arson, but no one seemed to notice. Disappointed with the absence of media coverage of their crimes, they decided to plan and execute a sensational "perfect crime" that would garner public attention, and confirm their self-proclaimed status as "supermen".