Ernst Wilhelm Oskar Windisch (4 September 1844, Dresden – 30 October 1918, Dresden) was a German scholar and celticist.
He is known as an Indo-Europeanist. He was also a friend of the young Friedrich Nietzsche.
- Compendium of Irish Grammar (1883 English translation)
- Zwölf Hymnen des Rigveda, mit Sayana's commentar (1883)
- Irische Texte, 4 vols. (1880-1909) with Whitley Stokes
- Iti-Vuttaka, editor
- Festschrift (1914)
- Kleine Schriften (2001) edited by Karin Steiner and Jörg Gengnagel