Anna of Poland (1366–1425) was countess consort of Celje, a medieval Slovenian feudal state, and an influential woman in politics of Poland.
She was daughter of King Casimir III of Poland (1309–1370), who was succeeded, not by Anna nor any of Casimir's own descendants, but by Casimir's nephew, King Louis I of Hungary. Anna's mother was Casimir's fourth wife Jadwiga of Żagań (d. 1390). Anna's elder half-sisters were already dead though one of them had left children. Anna was the eldest child of that fourth marriage, which did not either produce any sons to King Casimir's dismay.
In 1380 Anna was married to William, Count of Celje (1361–1392), a man chosen by Anna's first cousin, King Louis, from among his vassals in Hungarian south. They had a single surviving child, a daughter known as Anna of Celje (1386–1416). In 1394 the widowed Anna married secondly Ulrich, Duke of Teck (died 1432).
Meanwhile, the throne of Poland had passed in 1386 to Jogaila (Władysław IV Jagiełło), Grand Duke of Lithuania. When his first wife, the Queen Regnant Jadwiga of Poland (Anna's first cousin once removed) died in 1399 without surviving children, Władysław sought a wife among the heirs to the kingdom of Poland, which had been Jadwiga's inheritance. Duchess Anna desired to regain Poland for her heirs, the direct descendants of Casimir III, and to obtain power in her homeland. To achieve this, her young daughter Anna was married in 1401 or 1402 to the widowed Władysław Jagiełło, then aged around 50. She gave birth to a daughter, Princess Jadwiga of Lithuania, in 1408.
Anna of Poland, Duchess of Teck and Countess of Celje worked to advance her daughter's and her granddaughter's position in Poland. When her daughter Anna died in 1416, without further surviving children, Władysław married Elisabeth of Pilica in 1417, and then Sophia of Halshany in 1422, both of whom did not descend from the Piast kings of Poland, as he had been unable to find any more brides with a hereditary right to the kingdom. The king's two sons and heirs were born by his last wife, Sophia.
In 1421 Anna's granddaughter Jadwiga was betrothed to the future Frederick II, Elector of Brandenburg (1413–1471), the second son of Frederick I, Elector of Brandenburg. A party of Polish nobles, including Anna, wanted Jadwiga and her intended husband to succeed Władysław at least in Poland, instead of her half-brothers, his sons by Sophia.
Anna died in 1425, which left Jadwiga without any strong relatives to support her position. In 1431 Jadwiga died without any issue, allegedly by poison. In this way, Anna's descent became extinct before Władysław's death in 1434.