Harmonielehre is a 40-minute orchestral composition by the American composer John Adams, composed in 1985. In his memoir, Adams wrote that the piece "was a statement of belief in the power of tonality at a time when I was uncertain about its future" and that it was "a one-of-kind [sic] once-only essay in the wedding of fin-de-siècle chromatic harmony with the rhythmic and formal procedures of Minimalism".
The composition's title, German for "study of harmony", is a reference to Arnold Schoenberg's 1911 music theory textbook of the same name, a study of tonal harmony. Other theory texts titled Harmonielehre include those by Heinrich Schenker (1906) and Hugo Riemann (1893).