Ephraim Deinard (1846–1930) was one of the greatest Hebrew "bookmen" of all time. He was a bookseller, bibliographer, publicist, polemicist, historian, memoirist, author, editor, and publisher, all rolled into one.

Deinard produced some 70 volumes whose subjects range from Jewish history and antiquities (especially of the Crimea, Russia, America, and The Holy Land), to treatises against Hasidism, Christianity, and Communism, parodies, medieval and modern Hebrew literature, Jewish religion, and especially booklore.

Deinard's antiquarian activities, which involved constant travel throughout Europe, the Orient, and America, gave him a unique acquaintance with scholars, private collectors, fellow booksellers, and libraries. He came into contact and conflict with numerous Hebrew writers and Jewish communal and political figures. His wide-ranging knowledge and experience are fully reflected in his own voluminous writings, mostly in Hebrew, produced over more than half a century. His scope of interests, the intensity of his sentiments, the acerbity of his remarks, all coupled with his bibliophily, render Deinard's works a source of contemporary Jewish historical and literary controversy, as seen in the margins of the Hebrew-reading world, before and after World War I.