Eugene George Istomin (November 26, 1925 – October 10, 2003) was an American pianist.

Istomin was born in New York City of Russian parents. He was famous for his work in the piano trio, with Isaac Stern and Leonard Rose, known as the Istomin-Stern-Rose Trio, with whom he made many recordings, and particularly of music by Beethoven, Brahms and Schubert. He also played with them in orchestral music, with conductors such as Eugene Ormandy, Bruno Walter and also as a soloist.

His earliest public performances were from age 6 with his mother, and at 12 he entered the Curtis Institute. He studied under Rudolf Serkin and also Mieczysław Horszowski.

In 1943 he won the Leventritt award, and also the Philadelphia Youth Award. He made his debuts with the Philadelphia Orchestra with Eugene Ormandy, playing a concerto by Chopin, and the New York Philharmonic conducted by Artur Rodziński playing Brahms' Piano Concerto No. 2 in the same week in 1943.

He performed with Rodzinski and the New York Philharmonic a second time in December 1944, performing Beethoven's Fourth Piano Concerto.

He commissioned and premiered Roger Sessions' piano concerto in 1956. Several other composers, including Henri Dutilleux and Ned Rorem, wrote music for him.

He won a Grammy Award in 1970 with the trio, for their recordings of Beethoven.

He recorded extensively for Columbia (later Sony Classical) solo works and chamber music.

He married Marta Montañez Martinez (Marta Casals Istomin), the widow of Pablo Casals, on February 15, 1975. She is a former president of the Manhattan School of Music and former artistic director of the Kennedy Center for the Performing Arts in Washington, D.C. He moved to Washington in 1980.

In the 1980s and 1990s he gave recital tours in which he toured 30 American cities with his own pianos and piano tuner.

He received the French Légion d'honneur in 2001.

He died of liver cancer in 2003 at his home in Washington.