The Ossolineum or the National Ossoliński Institute is a Polish cultural foundation, publishing house, archival institute and a research centre of national significance founded in 1817. Located in the city of Wrocław since 1947, it is the second largest institution of its kind in Poland after the ancient Jagiellonian Library in Kraków. Its publishing arm is the oldest continuous imprint in Polish since the early 19th century. It bears the name of its founder, Polish nobleman, Count Józef Maksymilian Ossoliński.
Although its origin may be traced to the foreign imposed partitions of the Polish–Lithuanian Commonwealth in the 18th century, the institute's actual history dates from 1817 in the former Polish city of Lwów, then known as Lemberg, capital of Galicia, a province of Austria-Hungary. The institute first opened its doors to the public in 1817.