Wilhelm Ludwig Geiger (21 July 1856 – 2 September 1943) was a German Orientalist in the fields of Indo-Iranian languages and the history of Iran and Sri Lanka. He was known as a specialist in Pali, Sinhala language and the Dhivehi language of the Maldives. He is especially known for his work on the Sri Lankan chronicles Mahāvaṃsa and Cūlavaṃsa of which he made critical editions of the Pali text and English translations with the help of assistant translators.
He was born at Nuremberg, the son of an evangelical clergyman, and was educated especially at the University of Erlangen-Nuremberg under the Iranian scholar Friedrich von Spiegel. During his studies, he joined the fraternity Uttenruthia. After completing his Ph.D. thesis in 1878, he became a lecturer on ancient Iranian and Indian philology and then a master at a gymnasium. In 1891 he was offered a chair in Indo-European Comparative Philology at the University of Erlangen, succeeding Spiegel. His first published works were on ancient Iranian history, archaeology and philology. He travelled to Ceylon in 1895 to study the language. He appeared on a stamp in Sri Lanka, in 1989.
The physicist Hans Geiger, inventor of the Geiger counter, was his son.
- The Age of the Avesta and Zoroaster, co-authored with Friedrich Spiegel, translated into English by Dārāb Dastur Peshotan Sanjānā, London 1886.
- Civilization of the eastern Iranians in ancient times, with an introduction on the Avesta religion, translated into English by Darab Dastur Peshotan Sanjana, London 1885–1886.
- Zarathushtra in the Gathas, and in the Greek and Roman classics, co-authored with Friedrich Heinrich Hugo Windischmann; translated into English by Dārāb Dastur Peshotan Sanjānā, Leipzig 1897.
- The Dīpavaṃsa and Mahāvaṃsa and their historical development in Ceylon, translated into English by Ethel M. Coomaraswamy, Colombo 1908.
- The Mahavāmsa or the Great Chronicle of Ceylon, English translation assisted by Bode, Mabel Haynes, Pali Text Society, London 1912.
- Maldivian Linguistic Studies, Colombo 1919.
- The Language of the Väddās, Calcutta 1935.
- A Grammar of the Sinhala language, Colombo 1938.
- Pali Literature and Language, translated by Batakrishna Ghosh from the German original, Calcutta 1943. Revised by K. R. Norman under the title A Pali Grammar, Oxford 1994.
- Cūlavamsa : being the more recent part of the Mahāvamsa, English translation assisted by Christian Mabel Duff Rickmers, Colombo 1953.
- Culture of Ceylon in mediaeval times, edited by Heinz Bechert, Wiesbaden 1960.
- Wilhelm Geiger: Ceylon. Tagebuchblätter und Reiseerinnerungen, Wiesbaden 1898.
- Wilhelm Geiger und Ernst Kuhn (Hrsg.): Grundriß der iranischen Philologie, Trübner, Strassburg 1896.
- Wilhelm Geiger: Dipavamsa und Mahavamsa, die beiden Chroniken der Insel Ceylon, Erlangen, Leipzig 1901.
- Wilhelm Geiger: Dîpavamsa und Mahâvamsa und die geschichtliche Überlieferung in Ceylon, Leipzig 1905.
- Wilhelm Geiger und Magdalene Geiger: Pāli Dhamma vornehmlich in der kanonischen Literatur, München, 1920.
- Wilhelm Geiger: Elementarbuch des Sanskrit, de Gruyter, Berlin und Leipzig, 1923.
- Wilhelm Geiger: Besprechung zu Heinrich Junker, Arische Forschungen, um 1930.
- Wilhelm Geiger: Singhalesische Etymologien. Stephen Austin and Sons, 1936.
- Wilhelm Geiger: Beiträge zur singhalesischen Sprachgeschichte, Bayerischen Akad. der Wiss., München 1942.
- Wilhelm Geiger: Kleine Schriften zur Indologie und Buddhismuskunde, hrsg. von Heinz Bechert. Steiner,Wiesbaden 1973.
- Wilhelm Geiger: Die Reden des Buddha : Gruppierte Sammlung, Saṃyutta-nikāya, translation of Saṃyutta-nikāya, Beyerlein-Steinschulte, Stammbach, 1997.