Hieronim Ossoliński, (born ? – died 1575 or 1576), coat of arms Topór, was a Polish statesman, kasztelan of Sandomierz and Wojnicz, a delegate to the Sejm of 1569 and one of the signatories of the Union of Lublin, which formally united Poland and Lithuania into the Polish–Lithuanian Commonwealth. Ossoliński was a Calvinist, and a leader of Protestants in the province of Małopolska during the reign of king Zygmunt August. Ossoliński was also one of the leaders of the Executionist movement, which sought to reform 16th century Polish politics.