Walter Nelles (1883–1937) was an American lawyer and law professor. Nelles is best remembered as the co-founder and first chief legal counsel of the National Civil Liberties Bureau and its successor, the American Civil Liberties Union. In this connection, Nelles achieved public notice for his legal work on behalf of pacifists charged with violating the Espionage Act during World War I and in other politically charged civil rights and constitutional law cases in later years.
Walter Nelles was born April 21, 1883 in Leavenworth, Kansas, the son of George Thomas Nelles, a civil engineer. Nelles attended the prestigious Phillips Exeter Academy in Exeter, New Hampshire in preparation for an Ivy League collegiate education. Upon graduation from Exeter, Nelles enrolled in Harvard University, from which he graduated in 1905 with a Bachelor's degree.
After graduation, Nelles taught as an instructor at the University of Wisconsin from the fall of 1905 to the spring of 1907. Nelles then left Madison to return to Harvard, receiving a Masters degree in 1908 before moving on Harvard Law School. He graduated from Harvard Law with an LL.B. in 1911. During the period of his graduate education, Nelles also taught as an instructor at Lowell Institute and Radcliffe College.