The Party for the Open Society (Czech: Strana pro otevřenou společnost, SOS) is a minor social liberal political party in the Czech Republic.

In 1993 the party was renamed the Free Democrats (Czech: Svobodní Demokraté).

The party's political programme places highest importance on sustainable development.

In 2006 the SOS had local organisations in four of 13 regions in the Czech Republic, and in Prague.

SOS also supports the Club of Committed Non-Party Members and other liberal parties.