Career
Tomasz became Colonel of the Crown Army in 1765, Chamberlain of King Stanisław II Augustus in 1767, castellan of Czersk since 1777, Court Treasurer since 1791, Marshal of the Sejm of the Duchy of Warsaw in 1809 and later President of the Senate of the Duchy of Warsaw and the Kingdom of Poland. He was politically tied to King Stanisław II Augustus, and he also participated in the "Thursday dinners" held annually by the king in his palace in Warsaw. Son of Piotr Ostrowski and Konstancja Stoińska.
In 1764 he supported the election of King Stanisław II Augustus.
A true hero of the country, he restrained the king from accession to the Targowica Confederation and he was subsequently imprisoned by the Russians. In 1765, was a colonel in the royal army and became royal chamberlain in 1767.
Ostrowski became the castellan of Czersk in 1777. In 1788 he founded the metallurgical village of Tomaszowe Kuźnice, which was granted the status of an industry and trade village (osada fabryczno-handlowa) in 1824, designated a city in 1830 and was renamed to Tomaszów Mazowiecki.
In 1791 he was proclaimed the Treasurer of the Crown.
He was one of the founders of the Friends of the Constitution Assembly Government. During the Polish-Russian war, at the meeting of 23 July 1792 he strongly opposed the decision of King Stanisław II Augustus on his accession to the Confederation of Targowica and he enhanced to revolt against the Russians and the administration which had control over the Polish-Lithuanian Commonwealth. Later he became the Marshal of the Sejm of the Duchy of Warsaw in 1809 and later President of the Senate of the Duchy of Warsaw and the Kingdom of Poland.
He died on February 5, 1817 in Warsaw.