Italian claims to Dalmatia after the First World War. The whole establishment of Italy originally, however, itself involved much irredentism, as it unified areas belonging to various states one-by-one with the growing proto-Italian state.
The establishment of Germany, like Italy, involved a large amount of unification of areas belonging to numerous small states.
Greece's claims on areas of the ex-Ottoman Empire. After World War I Greece claimed what is now the Aegean coastline of Turkey, because of the predominance there of a Greek population since antiquity and former rule by the Byzantine Empire. Other Greek irredentist claims under the "Greater Greece" policy called Megali Idea included southern Albania (Northern Epirus) and Cyprus. Today, border changes are not a key topic of political discussion in Greece.
The claims of Bulgaria, Serbia, Greece and Montenegro on the European parts of the Ottoman Empire and Albania (both of which the four divided among themselves) before the First Balkan War, where they took these claims to the battlefield, and won.
Spanish claims to Gibraltar which was ceded in perpetuity to Britain in 1713 under the Treaty of Utrecht, and argues its case at the United Nations claiming its territorial integrity is affected.
Hungarian claims to parts of the neighbouring countries inhabited by the ethnic Hungarians (including parts of Slovakia, Romania, Serbia, Ukraine, etc.). The claim is based on historic criteria for some regions (such as Transylvania, where Hungarians are a majority in two out of sixteen counties), and ethnic for other regions. The former Kingdom of Hungary lost 2/3 of its territories as a result of the Treaty of Trianon in 1920. Nowadays, irridentists are split between a group which wishes to reclaim all former regions of Hungary, and those only desiring ethnic Hungarian regions that are contiguous to current-day Hungary.
Georgia (country) claims Tao-Klarjeti (a part of Turkey) as it's historic territory, due to the fact that the region has a large Georgian population and has been under Georgian rule for long periods of history, although there have been no official claims, many Georgians still claim it as a part of their country.
Irredentists from the Republic of Macedonia have expressed land claims to the entire region of Macedonia out of which only 40% lies within the Republic of Macedonia, the rest being in Greece, Bulgaria and Albania, on the purported ethnic, historical and geographic grounds.
Armenian claims to the Nagorno-Karabakh region of Azerbaijan on ethnic and perceived historical grounds. It is de jure part of Azerbaijan, but de facto an Armenian populated independent country where conflict started in 1988 and has the explicit long-term goal of rejoining Armenia. See also: Nagorno-Karabakh Republic
Armenian irredentists have also laid claim (on perceived historical, historical ethnic, modern ethnic and also juridical grounds) to territories up to the Pontic coast of Turkey near Trebizond, and south past Lake Van (sometimes far enough to incorporate the historical Subterranean region of Cilician Armenia, though this claim has now been abandoned for the most part), as well as Nakhichevan in Azerbaijan, Javakh in Georgia, and areas of Northwest Iran near Maku. See United Armenia concept for more info.
Chechenia (currently part of the Russian Federation) has occasionally laid claims on a region called Akkia (roughly the Auhovskiy rayon, in Russian), part of neighbouring Dagestan. Prior to the 1944 Chechen deportation to Kazakhstan, the region was part of Chechnya (then an autonomous region within the Soviet Union), which was abolished. It was given to Dagestan, and included all of the modern Novolak district as well as parts of the Kazbek district and the Khasavyurt district (including the city of Khasavyurt itself). Following the repatriation in 1958, Chechen autonomy was not restored in Akkia, and the Chechens were barred from returning there. In spite of this, Chechens have returned to Akkia, and according to the census, in 2002 there were nearly ninety thousand Chechens in Dagestan, primarily in Akkia.
Russian irredentism has three definitions, narrow, interim and broad.
Cambodia has claimed parts of the Mekong Delta that lie in present day Vietnam on the basis that the area, which was formerly part of the Khmer Empire, was artificially carved up by the French during the Colonial Period and given to South Vietnam upon French withdrawal. The area still is home to at least one million ethnic Khmers (the Khmer Krom) who claim to be persecuted by the Vietnamese.
Bolivian claims to coastal regions of Chile annexed after the War of the Pacific. More recently, president Evo Morales expressed disgust with the secession of Acre (1902), which later become a Brazilian state, saying that the Brazilians provoked the unrest and later paid Bolivia only "a horse's price" for the priceless land.