Which Queen Isabella are you looking for? There have been many women in history with that name and title! I've listed the best-known here, with the earliest first, and with links to biographies for the most prominent.
Isabella of Angoulême (1187-1246): King John of England divorced his first wife to marry her when she was 12 or 13. The ensuing war with her previous fiance, Hugh of Lusignan, and with the King of France, resulted in John losing his French possessions. Isabel was the mother of Henry III of England.
Isabella I, Queen of Jerusalem (1192-1205): married four times, she succeeded her father Almaric I and her sister Sibyl to the throne and was succeeded by her daughter, Marie of Monteferrat.
Isabella of France (1292-1358), queen consort of Edward II of England: with her lover, Roger Mortimer, she helped depose Edward II and murder him.
Isabella of Bavaria (1371-1435): queen consort of Charles VI of France and his regent during his periods of madness.
Isabella of Portugal (1428-1496): second wife of John II of Castile, and mother of Isabella I of Castile and Aragon.
Isabella of Portugal (1503 - 1539): wife of Charles V, Holy Roman Emperor, she was regent for him in Spain for a number of years before she died in childbirth during one of his absences.
Isabella I of Castile and Aragon (1451-1504): also known as Isabella of Castile, Isabella of Spain, Isabella the Catholic, Isabel la Catolica: she ruled with her husband Ferdinand, drove the Moors from Granada, expelled unconverted Jews from Spain, sponsored Christopher Columbus' voyage to the New World, established the Inquisition -- and more.
Isabella Clara Eugenia (1566 - 1633): Infanta of Spain, Archduchess of Austria, ruler of the Spanish Netherlands with her husband, Archduke Albert.
Isabella Farnese (1692-1766): queen consort of Philip V of Spain. Her active role in foreign and domestic policy made her unpopular.
Isabella II of Spain (1830-1904): Bourbon queen whose role in the Affair of the Spanish Marriages added to the 19th century's European turmoil.
More women's history biographies, by name: