The Union and Security Act (Swedish: Förenings- och säkerhetsakten, Finnish: Yhdistys- ja vakuuskirja), alternatively Act of Union and Security, was proposed by king Gustav III of Sweden to the assembled Estates of the Realm during the Riksdag of 1789. It was a document, adding to the Swedish Constitution of 1772 new provisions. The King strengthened his grip on power while at the same time riding on a popular wave that also meant a decrease in aristocratic power. It has been described as "fundamentally conservative".