R..Yom Tov ben Abraham Ishbili of Seville; known as Ritba, from the initial letters of his Hebrew name Rabbi Yom Tov Ben Abraham; c. 1250–1330 was a Spanish talmudist. Famous already in his youth as a scholar, he studied in Barcelona under R. Aaron ha-Levi of Barcelona and R. Solomon b. Abraham Adret, and was mentioned in an official document of 1280 of the kingdom of Aragon as a hakham and dayyan of the community of Saragossa. Even during the lifetime of his teachers, questions were addressed to him for he was regarded as among the leading Spanish rabbis.

After the death of his teachers, he was regarded by Spanish Jewry as its spiritual leader. When the community of Daroca introduced certain decrees, it was stated that this was done "in the name of R. Asher [b. Jehiel] and in that of R. Yom Tov b. al-Ishbili" (Resp. Ritba, no. 159). His bet din was referred to by contemporary rabbis as "the great and excellent bet din" (ibid., no. 43). In his humility, he would apologize if he thought he had used somewhat harsh language in writing to anyone who disagreed with his views (ibid., no. 208). He devoted himself also to the study of philosophy, in particular Maimonides' Guide of the Perplexed, acquiring a thorough knowledge of it and comparing its translation with the Arabic original. He also studied the works on logic of the Provencal scholars R. Samuel ibn Tibbon, R. Jacob Anatoli, and R. Gershom b. Solomon.

R. Yom Tov's reputation rests upon his novellae to the Talmud, Hiddushei ha-Ritba. He apparently began writing them from the direct dictation of his teacher R. Aaron ha-Levi . When, however, he realized that the work would be inordinately long, he decided to make an abbreviated version. There is even a possibility that he wrote a third "version" to some tractates. These facts give rise to a difficult and complicated literary problem, his novellae to the different tractates being of different "types," and therefore not always of the same quality. It is sometimes very hard to identify them with certainty. His novellae are, in general, very rich in early source material: tosafistic, Spanish, Provençal, and geonic, and display a considerable originality, though he is very much under the influence of his two great teachers.

His novellae have been published many times, and in different editions. His other works include: a commentary on Hilkhot Nedarim by Nahmanides (in Ishei ha-Shem, Leghorn, 1795); Hilkhot Berakhot (at the end of Hayyim Isaac Musafia's responsa Hayyim va-Hesed, 1844); Responsa (ed. by Y. Kafah, 1959); Sefer ha-Zikkaron (by S. H. Halberstamm, in Hiddushei ha-Ritba al Niddah, 1868; critical edition by K. Kahana, 1956); a commentary on the Passover Haggadah in Peh Yesharim (1838); Perush al Hilkhot ha-Rif, in manuscript: Sefer ha-Derashot, his homilies, now lost.