Princess Elżbieta Izabela Czartoryska (21 May 1736– 11 November 1816), better known under her married name Izabela Lubomirska, was a Polish noblewoman.

She was the daughter of August Czartoryski, one of the leaders of the Familia, and Maria Zofia Czartoryska. In her youth she loved her cousin, Stanisław August Poniatowski, later king of Poland, but was unable to marry him due to the objections of her father, who thought him not sufficiently rich or influential. Eventually, she married Stanisław Lubomirski on 9 June 1753, with whom she had four children: Julia, Konstancja, Elżbieta, and Aleksandra.

She was a member of an adoptive Masonic lodge. Because of her liking for blue, which she often wore, she was called the "Blue Marquise".