This chapter addresses, albeit briefly, some salient moments of the international projection of Russia and Ukraine, focusing in particular on the role of Moscow as a nuclear power, as well as on the Russian-Ukrainian bilateral dynamics, also in relation to the broader picture of the post-Soviet space . Therefore, after having reconstructed some crucial phases of the post-Soviet transition, this contribution focuses on relations with the European Union in the period between the nineties and the beginning of the new millennium, during which the community strategy of "new neighborhood" began , to face, therefore, the repercussions produced by the Eastern enlargements of the EU and NATO, the subsequent, growing multipolar reorientation of the Kremlin's international strategies, accompanied by a growing dispute not only between Moscow and Kiev (resulting in a military conflict in 2022), but also by a radical divergence in relations between Russia and Ukraine, with further, and profound, repercussions on the relations between these two countries and the Euro-Atlantic institutions.