Arnold Steinhardt (born 1937 in Los Angeles, California), is an American violinist, best known as the first violinist of the Guarneri String Quartet.
Steinhardt made his debut with the Los Angeles Philharmonic Orchestra at the age of 14. He studied at the Curtis Institute of Music in Philadelphia with Ivan Galamian and later in Switzerland with Joseph Szigeti and Toscha Seidel. In 1958 he won the Leventritt International Violin competition. After winning Leventritt, he was invited by George Szell to take second chair in the Cleveland Orchestra's first violin section (next to concertmaster Josef Gingold). He was later appointed to the faculty of the Curtis Institute, Rutgers, the State University of New Jersey, and University of Maryland. In 2009 he was appointed to the faculty of the Colburn School in Los Angeles. He has also performed extensively as a soloist.
He lives in New York City, and is the author of two books; Indivisible by Four: A String Quartet in Pursuit of Harmony, an account of his life in the Guarneri String Quartet, and Violin Dreams, an autobiography about his life and experiences as a violinist.