Princess Apolonia Poniatowski (17 January 1736 – 1814) was a Polish noblewoman, the sister-in-law of the King of Poland, Stanisław August Poniatowski.

She was the daughter of Bazyli Ustrzycki (1715-1751), castellan of Przemyśl and his second wife, Katarzyna Zielonka (b.1715).

In 1763, her brother-in-law was elected king of Poland.

She became the mother of Stanisław, Grand Treasurer of Lithuania, and Konstancja Poniatowska.

Her husband was known for his love life and was famously one of the clients of Henrietta Lullier.