The October Diploma was a constitution of the Austrian Empire adopted by Habsburg Emperor Franz Joseph on 20 October 1860. The Diploma was written by the Minister of Interior, Agenor Gołuchowski. It attempted to increase the power of the conservative nobles by giving them more power over their own lands through a program of aristocratic federalism. This policy was a failure almost from the start, and Franz Joseph was forced to make further concessions in the February Patent of 1861. Even so, historians have argued that the October Diploma began the "constitutional" period of the empire.

The Austrian Empire, officially known as the Empire of Austria, was a multinational European great power from 1804 to 1867, created by proclamation out of the realms of the Habsburgs. During its existence, it was the third most populous monarchy in Europe after the Russian Empire and the United Kingdom. Along with Prussia, it was one of the two major powers of the German Confederation. Geographically, it was the third-largest empire in Europe after the Russian Empire and the First French Empire.