Leopold Nowak (Vienna, Austria, 17 August, 1904 - May 27, 1991) Musicologist, chiefly known for editing works by Anton Bruckner. Reconstructed some of the latter's works to be as close to the composer's original, most of which had been revised and edited many times.

Nowak studied piano and organ at the Vienna Academy. He studied musicology with Adler and Lach at the Vienna University, where he later taught from 1932 to 1973.

He succeeded Robert Haas as music director of the music collection of the Austrian national library, in 1946, and is credited with helping preserve documents about Bruckner.

Nowak's approach to editing Bruckner's music was much more scientific than Haas's. Whereas Haas combined bits from the 1887 and 1892 versions of Bruckner's Symphony No. 8 in C minor to make his edition of the work, Nowak put out two separate editions for the two versions. Nowak also wrote essays examining theoretical aspects of the music of Bruckner and others, such as an essay on the metrical and rhythmical aspects of the Symphonies of Beethoven and Bruckner.

Nowak worked on a new edition of Wolfgang Amadeus Mozart's famously uncompleted Requiem in D minor, and was able through detailed scrutiny to distinguish Mozart's own handwriting from that of Süßmayr and Eybler to an extent no one had been able to do before. In recognition, Nowak was awarded the Goldene Mozart Medaille in 1985.

Nowak also studied the music of Heinrich Isaac, Joseph Haydn, Austrian church and folk music, and various Austrian composers from the Middle Ages (1480s onwards).

His work on Bruckner's music, particularly the Finale of Bruckner's Symphony No. 9 in D minor, is being continued by William Carragan .