Sha’ar HaMayim HaArokh is a short 13th-century compilation of laws about the mikvah (ritual bath) by the Rashba (Rabbi Shlomo ben Avraham ibn Aderet). It presents rulings, explanation, and analysis of topics like valid sources of water for a mikvah and conditions that disqualify a mikvah. The Rashba later wrote a condensed version, the Sha’ar HaMayim HaKatzar, in which he only presented the actual laws. These works are found in the back of some manuscripts of the Rashba’s Torat haBayit and are quoted by commentators like the Rivash, the Tashbetz and the Beit Yosef.