The Diplomatic Revolution was a reversal of European alliances between the War of the Austro-Hungarian Succession and the Seven Years War, with Britain and Austria breaking their alliance, France and Prussia breaking theirs, and the two sets reversing so that Britain and Prussia stood ready to fight France and Austria. This was also known as the Stately Quadrille and the Great Change of Partners.
France and Austria had been enemies by dint of tradition before the Diplomatic Revolution. This event reshaped the political landscape of Europe and set the stage for the Seven Years War, which broke out soon after negotiations had concluded and alliances had been, for the moment, decided.
Austria's alliance with Britain during the War of the Austro-Hungarian Succession had exacted a severe toll on Austrian resources. The British claimed rich prizes for themselves and the Austrians were not keen to go through the process again. Prussia had also seen gains during the war, a development feared by Austrian diplomats and royals.
Britain thought to balance out French power with a bolstered Prussia and so rearranged their loyalties accordingly. France sought to overbalance Britain's constant meddling in the Balance of Power, a prominent concept in political thought at the time, and so joined its fortunes to Austria's.