The Congress system is a diplomatic process adhered to between 1815 and 1822, under which all matters of international importance were discussed at meeting of all European powers in order to insure uniform action on the part of all concerned. The creator and great proponent of this system was the Viscount Castlereagh.

The system was established in the Congress of Vienna and led to the subsequent Congress at Aix-la-Chapelle in 1818, Congress at Troppau in 1820, Congress at Laibach in 1821, and the Congress of Verona in 1822.

The last congress was held in St. Petersburg in 1825 but by then the system had broken down and was virtually useless.