Hardy Boys, fictional brothers Frank and Joe Hardy, the teenage protagonists of a series of American juvenile mystery novels first published in 1927.
Frank and Joe are trained in the art of criminal detection by their father, Fenton, a former police detective. The boys solve crimes together, often aided by their father or their friends. Edward Stratemeyer originally conceived and plotted the series. More than four dozen novels about the Hardys were written by “Franklin W. Dixon”—the pseudonym used by a series of writers—and were distributed by the Stratemeyer Literary Syndicate. Publication of the series was continuous from 1927, when The Tower Treasure and two other Hardy Boys books were first issued. A Hardy Boys Casefiles series was published in 1987–98 and averaged about 10 titles per year. From 1988 to 1998 Dixon and the likewise pseudonymous Carolyn Keene were responsible for another series, The Nancy Drew–Hardy Boys Super Mysteries, which featured the Hardy Boys and Nancy Drew working together. The brothers were also teamed relatively briefly with Tom Swift (two books, 1992, 1993) and appeared in a series for younger readers called the Clues Brothers (1997–2000). In 2005 the Hardy Boys once again were updated and repackaged as the Undercover Brothers. It ended in 2012, and a new series, The Hardy Boy Adventures, debuted the following year.
The Hardy Boys were also featured in three American television series in the 1950s, an animated series that ran from 1969 to 1971, and a third series, The Hardy Boys/Nancy Drew Mysteries, in 1977–79. Another series ran in 1995.