Gary Mokotoff (born April 26, 1937) is an American genealogist who focuses primarily on Jewish genealogy. He is the first person to receive the Lifetime Achievement Award of the International Association of Jewish Genealogical Societies for which he was president (1989–1995).[1] He is the author/coauthor of a number of books including Where Once We Walked, a gazetteer which provides information about 23,500 towns (citing 37,000 place names) in Central and Eastern Europe where Jews lived before the Holocaust, How to Document Victims and Locate Survivors of the Holocaust, and Getting Started in Jewish Genealogy. He was co-editor of Avotaynu Guide to Jewish Genealogy.

Mokotoff is also known for his application of computers to genealogy. Among his accomplishments is co-authorship of the Daitch–Mokotoff Soundex System; the JewishGen Family Finder, a database of ancestral towns and surnames being researched by some 84,000[4] Jewish genealogists throughout the world and the Consolidated Jewish Surname Index.

He is co-owner of Avotaynu, a company that publishes books of interest to Jewish genealogical researchers as well as the journal Avotaynu.[5] He is/was on the Board of Directors of a number of organizations including the International Association of Jewish Genealogical Societies,[6] Federation of Genealogical Societies (FGS), Association of Professional Genealogists, Jewish Book Council, Association of Jewish Book Publishers, and JewishGen.

He was a pioneer of the computer software industry, joining IBM in 1959. He developed systems software that IBM supplied with its early commercial computer, the IBM 1401.