Same-Sex Unions in Pre-Modern Europe (UK title: The Marriage of Likeness: Same-Sex Unions in Pre-Modern Europe) is a historical study written by the American historian John Boswell and first published by Villard Books in 1994. Then a professor at Yale University, Boswell was a specialist on homosexuality in Christian Europe, having previously authored three books on the subject. It proved to be his final publication, released in the same year as his death.