Ernest Klein, OC (July 26, 1899 - February 4, 1983) was a Romanian-born Canadian linguist, author, and rabbi.
Klein was born in Szatmárnémeti (present-day Satu Mare), in Partium — a region of Austria-Hungary at the time, it is now in Romania; he received his PhD at the University of Vienna in 1925. He was the rabbi of the Nové Zámky community, Czechoslovakia, from 1938 Érsekújvár, Hungary, now Slovak Republic, from 1929 to 1944. In 1944, he was deported to Auschwitz and later to the Dachau concentration camp, where he was liberated. After the war he served as rabbi in Satu Mare. After emigrating to France, he was a rabbi of the synagogue on Rue de Montevideo in Paris (1950–1951) and in 1952 he emigrated to Canada, where he held the post of Rabbi of Congregation Beth Yitshak in Toronto until his death.
He is the author of A Comprehensive Etymological Dictionary of the English Language (1966–1967).
He is also the author of A Comprehensive Etymological Dictionary of the Hebrew Language for Readers of English (1987), an English-language etymological dictionary of Hebrew to which he devoted the last ten years of his life.
In 1978, he was made an Officer of the Order of Canada.