Although the Constitution of San Marino is technically older, the Poland’s Constitution of 3 May 1791 is generally considered the world’s second oldest modern constitution and the oldest in Europe.
The 1791 Constitution set out to establish a more effective constitutional monarchy, that had a clear division of executive, legislative, and judiciary powers.
Poland’s later constitutions take inspiration from the ideas in the Constitution of 3 May 1791. Poland’s modern constitution was put into effect in 1997 and it was last amended in 2009.