Rabbi Judah ben Yom Tov (Hebrew: יהודה בן יום טוב) was one of the Baalei Tosafot in France, a member of Rashi's family.
His father was Rabbi Yom Tov of Falaise, who was the son of Judah ben Nathan (known as Rivan), Rashi's son-in-law.
He married the widow of Isaac ben Meir (known as (Rivam), the brother of Rashbam and Rabbeinu Tam, who was a cousin of his father, Rabbi Yom Tov.
His grandson was Rabbi Judah ben Isaac Messer Leon.
In "Ohr Zarua" by Isaac ben Moses of Vienna, cites a responsa of Rashbam where he discussed Halakha before the elders of Paris, among them Rabbi Yehuda Bar Tov.