queen of Poland (1384–99) whose marriage to Jogaila, grand duke of Lithuania ( Władysław II Jagiełło of Poland), founded the centuries-long union of Lithuania (Lithuania, grand duchy of) and Poland.

Jadwiga was the daughter of Louis I, king of both Hungary and Poland, and Elizabeth of Poland. After Louis died on September 11, 1382, his elder daughter, Maria, was elected queen of Hungary, but the Poles opted to end the personal union between the two countries by choosing Jadwiga as their queen, though she was then but a child of nine years. On October 15, 1384, she was crowned rex (“king”) of Poland. The Polish magnates further promoted her marriage to Jogaila in order to produce a union of territories larger than the former one with Hungary, and this new entity altered the balance of power in central Europe. The marriage also opened the way to the Christian conversion of the largely pagan Lithuanians. Jogaila was baptized in Kraków on February 15, 1386, married to Jadwiga on February 18, and crowned on March 4. While Jadwiga lived, however, she and her husband ruled jointly, with Jadwiga remaining the leading personality in the realm. She died in childbirth and without heir; her husband was then able to assert his authority in Poland.

A patron of religion and scholarship, Jadwiga sought to promote the religious development of the nations that she had united, founded a special college for Lithuanians in Prague, and financed the restoration of the university at Kraków, which was effected after her death and later named the Jagiellonian University. Chiefly Jadwiga's work, the university was modeled after the University of Paris and became the centre of Polish civilization and influence.

Jadwiga was canonized by Pope John Paul II in Kraków on June 8, 1997.