William Abbott Oldfather (23 October 1880 – 27 May 1945) was an American classical scholar. He was influential for building strong academic traditions in classical studies at the University of Illinois and for his studies of ancient Locris in Greece.
William Oldfather was born in 1880 to American parents stationed in Urumiah, Persia (now Reza'iyeh, Iran or Urmia, Iran). His parents were Presbyterian missionaries, Jeremiah Oldfather and Felicia (née Rice). His father's paternal immigrant ancestor had immigrated from Germany in 1770 before the American Revolution and his mother's ancestors included pioneer explorer Daniel Boone. His younger brother was Charles Henry Oldfather (1887–1954), who also became a classical scholar. He was noted for many translations, and they sometimes worked together.
In 1890 the family returned to the United States, working in Harmony, Indiana. Oldfather attended local schools and did his college work at Hanover College, with a second bachelor's degree completed at Harvard College, followed by a master's degree.
He married Margaret Agnes Giboney in 1902; they had two daughters. He started his academic career teaching Classics at Northwestern University, and studying deeply in important German scholarship. In 1906 he traveled to Germany for additional graduate work; he was awarded a doctorate by the University of Munich in 1908. He studied with Hellenist Otto Crusius, the Latinist Fredrich Vollmer, historian Robert von Pöhlmann; and archeologist and art historian Adolph Fürtwangler. Oldfather was strongly influenced by his studies in Germany: he became a great admirer of German scholarship, nearly bilingual in the language, and sympathetic to the Socialist cause.
Returning to the United States, Oldfather worked for a year at Northwestern before moving to the faculty of the University of Illinois in 1909. In 1910, he and Arthur Stanley Pease worked together to create what is now the Classics Library Collection. Becoming a full professor in 1915, he served as "Czar of Classics" and made numerous contributions. He was head of his department from 1926 to his death in 1945. Among his students was the classisist Richmond Lattimore.