Windisch, Wilhelm Oscar Ernst (1844–1918), Sanskrit and Pali scholar and celticist, was born 4 September 1844 in Dresden, Germany, son of a teacher, was educated at the Kreuzschule in Leipzig, and went on to Leipzig University (1863), where he studied classical and comparative philology. He came under the influence there of Georg Curtius, and of Hermann Brockhaus, who first impelled him in the direction of Celtic studies. He finished his doctorate in 1867 on the major Homeric hymns, and became master of the Thomas School at Leipzig in the following year. In 1869 he was appointed Privatdozent in Sanskrit and comparative philology in Leipzig, but during 1870–71 he was called to London, where he was employed by the India Office in cataloging Sanskrit manuscripts. There he met Standish Hayes O'Grady (qv), with whom he remained a lifelong friend. It was O'Grady who introduced Windisch to the study of living Irish, to which he made such an outstanding contribution.
Windisch spent some time in Ireland in 1871, where he met Whitley Stokes (qv) at his father's house in Dublin, and, as he said in his foreword to Stokes's posthumous edition of Cath Cathardha, ‘since then the friendship with him has been a part of my life's happiness’. Returning to Germany in 1871, he was appointed professor extraordinarius at Leipzig and elected to the RSAI (1872). He was made ordinarius in comparative philology at Heidelberg in 1873, and professor ordinarius at Strasburg in 1875, where he held the first Irish course ever offered at a university. He returned to Leipzig in 1877 as professor of Sanskrit, in which position he remained until his death. He was rector there 1895–6.
Although his contributions to Sanskrit and Pali studies – more than 300 – far outnumber those in Celtic studies (thirty-six), it is for his remarkable contributions to Old and Middle Irish lexicography that he will be best remembered among celticists. It has been said that ‘what Zeuss did for Old Irish, Windisch did for the in some ways more complicated subject of Middle Irish’ (Knott, 1919). His fundamental researches were published in Irische Texte (i–iv, 1880), establishing the basis for the scientific study of the sagas and early poetry. His editions were based on the most careful attention to the readings of the manuscripts, with minute registration of all variants and complete glossaries. He published a Concise Old Irish grammar in 1879. Perhaps his finest contribution to Celtic studies was his edition of the Book of Leinster text of ‘Táin Bó Cuailnge’ (1905). His last contribution to Celtic studies came in 1912 with his edition of the Egerton text of the ‘Táin’. He died 30 October 1918 at Leipzig, having corrected the proofs of his History of Sanskrit philology. It has been said by one who knew him that ‘those who had the privilege of meeting him will treasure the remembrance of a refined and gentle spirit, free from all bitterness and self-esteem’ (Flower).
Some time after becoming rector of Leipzig University, he married the daughter of the economist Wilhelm Roscher; they had a large family. One of his sons, Hans Windisch, subsequently became professor of theology at Leipzig.