Since 2012, there has been a rise in the assertiveness of both China and Russia’s foreign policies. Both countries have framed their actions as justifiable for various reasons including: historical claims; the assertion of territorial sovereignty rights; or, in coming to the aid of an ally. What is most concerning is the nationalistic rhetoric which has accompanied these actions with its central focus on the attainment, or re-establishment, of great power status. Both President’s Xi and Putin contend that this status is a vital part of their countries national identities. Because of the close association between nationalism and the attainment of great power status both China and Russia have become more willing to challenge the international status quo which has led to a rise in great power competition. As a result, they now represent the first revisionist challenge to the liberal international order since the demise of the Soviet Union. This research investigates the impact of contemporary nationalism on revisionist great powers, and does it increase their threat to the international order? This thesis aims to contribute to the current literature on Chinese and Russian nationalism and how nationalism drives the foreign policy choices of both countries. Whilst work has been done on contemporary nationalism, there is a limited amount that examines its impact on the foreign policy of great powers. Through a case study analysis of China’s foreign policy regarding the South China Sea, the East China Sea and Taiwan, this thesis has investigated if nationalism is responsible for China’s more assertive policy in these instances. Similarly, a case study analysis of Russia’s foreign policy is applied to the Ukraine, Syria and the Arctic to see if nationalism is responsible for Russia’s more robust foreign policy which has resulted in their annexation of the Crimea; their involvement in the Syrian civil war; and the modernisation of their armed forces and attendant military build-up in the Arctic. The thesis concludes that nationalism largely drives and frames Beijing and Moscow’s foreign policy choices and that both the Chinese and Russian leaders use it for four principal reasons. First, to frame their interests with regards to their territorial integrity. Secondly, as a means to unite the populace around a national goal or objective. Thirdly, as a means to strengthen and legitimise their authoritarian regimes in the face of Western democratic ideals. Lastly, as a way to compensate for failures in their performance legitimacy.