In February and March 2014, Russia invaded and subsequently annexed the Crimean Peninsula from Ukraine. This event took place in the aftermath of the Revolution of Dignity and is part of the wider Russo-Ukrainian War.

The events in Kyiv that ousted Ukrainian president Viktor Yanukovych sparked demonstrations against the new Ukrainian government. At the same time Russian president Vladimir Putin discussed Ukrainian events with security service chiefs remarking that "we must start working on returning Crimea to Russia". On 27 February, Russian troops captured strategic sites across Crimea. This led to the installation of the pro-Russian Aksyonov government in Crimea, the Crimean status referendum and the declaration of Crimea's independence on 16 March 2014. Although Russia initially claimed their military was not involved in the events, it later admitted that they were. Russia formally incorporated Crimea on 18 March 2014.

Following the annexation, Russia escalated its military presence on the peninsula and made nuclear threats to solidify the new status quo on the ground.

Ukraine and many other countries condemned the annexation and consider it to be a violation of international law and Russian agreements safeguarding the territorial integrity of Ukraine. The annexation led to the other members of the then-G8 suspending Russia from the group and introducing sanctions. The United Nations General Assembly also rejected the referendum and annexation, adopting a resolution affirming the "territorial integrity of Ukraine within its internationally recognised borders".

The Russian government opposes the "annexation" label, with Putin defending the referendum as complying with the principle of the self-determination of peoples.