The Well of Loneliness is a lesbian novel by British author Radclyffe Hall, it follows the life of Stephen Gordon, an Englishwoman from an upper-class family whose sexual inversion is apparent from an early age. She finds love with Mary Llewellyn, whom she meets while serving as an ambulance driver in World War I, but their happiness together is marred by social isolation and rejection, which Hall depicts as typically suffered by inverts, with predictably debilitating effects.

Publicity over The Well of Loneliness's legal battles increased the visibility of lesbians in British and American culture. For decades it was the best-known lesbian novel in English, and often the first source of information about lesbianism that young people could find.

Although critics differ as to the value of The Well of Loneliness as a work of literature, its treatment of sexuality and gender continues to inspire study and debate.