Louis Marshall (December 14, 1856 – September 11, 1929) was an American corporate, constitutional and civil rights lawyer as well as a mediator and Jewish community leader who worked to secure religious, political, and cultural freedom for all minority groups. Among the founders of the American Jewish Committee (AJC), he defended Jewish and minority rights. He was also a conservationist, and the force behind re-establishing the New York State College of Forestry at Syracuse University, which evolved into today's State University of New York College of Environmental Science and Forestry (ESF).

Louis Marshall was born on December 14, 1856, in Syracuse, New York, to two Jewish immigrants, recently arrived from Germany. Founded just eight years earlier, in 1847, Syracuse was a booming transportation, financial, and manufacturing hub on the Erie Canal, as the United States expanded West. On the brink of the American Civil War, the city was also a well-known stop on the Underground Railroad.

Marshall's father, Jacob Marshall, had arrived in New York City at 19 years of age on September 1, 1849, from Neidenstein, Bavaria, in Germany; his mother arrived from Württemberg, Germany, in 1853. According to Louis Marshall, the family name had been spelled "Marschall", with a "c", in "Rhenish Bavaria ... near the French boundary". Marshall's friend and colleague, Cyrus Adler noted in his remembrances of Marshall that the latter's "father migrated to the United states in 1849, the year which marked the beginning of migration from Germany following the failure of the revolutionary movements of 1848." From New York City, Jacob Marshall had "worked his way up the Erie Canal to Syracuse, where he opened a hide, fur, and leather business. It was marginally profitable."

Louis was the eldest of six children. He had one brother, Benjamin, two years younger, and four sisters: Marie, Bertha, Clara, and Ida; 13 years separated Louis and his youngest sister, Ida. The family resided at 222 Cedar Street, "in the old Seventh Ward of Syracuse", an area today approximately where the Onondaga County Justice Center (county jail) is located.

From childhood, Marshall was both a scholar and a linguist. His first language was German: "I spoke German before I knew a word of English, and so long as my mother lived (she died in 1910) I never spoke to her otherwise than in German." Louis' mother, Zilli (or Zella), was "well educated for her times ... reading to [her children] in German, Schiller, Scott and Hugo, the standard literature of mid-century."

Marshall attended "the Seventh Ward Public school" and later Syracuse High School, from which he graduated in 1874, one of eight males in a graduating class of 22. In addition he attended German and Hebrew schools along with his sisters. In his various school settings, Marshall applied himself to studying French, German, Latin, Greek and Hebrew. The latter he also learned from his father. Later in life, Marshall taught himself Yiddish.

Upon high school graduation, Marshall "began the study of law, in accordance with the fashion of that day, in a lawyer's office, that of Nathaniel B. Smith", where he served a two-year apprenticeship. This under his belt, his next step towards a career in law was to "enroll in Columbia University's law school (then Dwight Law School)". According to Marshall, "I really do not know if I am considered an alumnus of the Law School at Columbia University or not. If I am, then it is very peculiar that it has not been until I arrived at the mature age of seventy-two that I should have received a letter which is addressed to me as a 'Dear Fellow Alumnus'. I attended the Law School from September, 1876, to June, 1877. ... I never received a degree because two years actual attendance was required."

After completing his legal studies on January 1, 1878, Marshall joined the law firm of William C. Ruger in Syracuse. A few years later, in 1885, he became a member of the New York State Bar Association. According to Adler, "the day he was admitted to the Bar, Marshall became a partner in Ruger's firm". Later, when Ruger was appointed chief justice of the New York State Court of Appeals, "the law firm became Jenny, Brooks & Marshall." During this period, Marshall rose to prominence not only in New York, but nationally: "In 1891 he was part of a national delegation that asked President Benjamin Harrison to intervene on behalf of persecuted Russian Jews." Before the age of 40, Marshall had argued over 150 cases before the Court of Appeals.