Buin Zahra (, also Romanized as Bu’in Zahra; also known as Buin , also Romanized as Bu’in and Buyin) is a city in and capital of Buin Zahra County, Qazvin Province, Iran. At the 2011 census its population was 18,000. Most of the population of Buin Zahra belong to the Tat ethnic group and they speak Tati language.