Russian irredentism

Russian irredentism refers to irredentist claims to parts of the former Russian Empire or the Soviet Union made during the 21st century for the Russian Federation. 
The annexation of Crimea is an example of an irredentist claim.
History.
Russian Empire.
From roughly the 16th century to 20th century, the Russian Empire followed an expansionist policy. Few of these actions had irredentist justifications, though the conquest of parts of the Ottoman Empire in the Caucasus to bring Armenian Christians under the protection of the Tsar may represent one example.
Post-Soviet Union (21st century).
After the dissolution of the USSR in 1991, it was thought that the Russian Federation gave up on plans of territorial expansion or kin-state nationalism, despite some 25 million ethnic Russians living in neighboring countries outside Russia. Stephen M. Saideman and R. William Ayres assert that Russia followed a non-irredentist policy in the 1990s despite some justifications for irredentist policies—one factor disfavoring irredentism was a focus by the ruling interest in consolidating power and the economy within the territory of Russia. Furthermore, a stable policy of irredentism popular with the electorate was not found, and politicians proposing such ideas did not fare well electorally. Russian nationalist politicians tended to focus on internal threats (i.e. "outsiders") rather than on the interests of Russians outside the federation.
It has been proposed that the annexation of Crimea in 2014 proves Russia's adherence to irredentism today. 
The annexation of Crimea led to a new wave of Russian nationalism, with large parts of the Russian far right movement aspiring to annex even more land from Ukraine, including the unrecognized Novorossiya. Vladimir Socor proposed that Vladimir Putin's speech after the annexation of Crimea was a "de facto" "manifesto of Greater-Russia Irredentism". However, after international sanctions were imposed against Russia in early 2014, within a year the "Novorossiya" project was suspended: on 1 January 2015, the founding leadership announced the project has been put on hold, and on 20 May the constituent members announced the freezing of the political project.
Some Russian nationalists seek to annex parts of the "near abroad", such as the Baltic states, while some fear potential escalation due to Russian irredentist aspirations in northern Kazakhstan also.