Hai Dat (Հայ Դատ, "Armenian Cause") is the diaspora-anchored political programme that crystallised after 1923, when the Treaty of Lausanne erased the territorial and minority provisions of Sèvres and left the survivors of the Armenian Genocide without juridical redress. Its three classical demands are: (1) international recognition of the genocide, (2) just reparations (hatutsumneru hartz), encompassing both restitution of communal and individual property and compensation, and (3) territorial restoration, traditionally formulated as the boundaries of "Wilsonian Armenia" awarded by President Woodrow Wilson's arbitral decision of 22 November 1920.

Hai Dat is the animating cause of the post-1923 Armenian Revolutionary Federation in exile, institutionalised through the ARF's national committees (Hai Dat offices) in Beirut, Paris, Washington, Yerevan and elsewhere; the Armenian National Committee of America (ANCA) is its principal lobbying vehicle in the United States. Its operational repertoire includes legislative recognition campaigns (France 2001, Germany 2016, US 2019, Biden 2021), litigation (insurance restitution suits against New York Life and AXA in the 2000s), commemoration (24 April mobilisations), and at the radical fringe in 1975–91 the armed campaigns of the ASALA and JCAG, which Hai Dat as a movement has formally disavowed.

Hai Dat's relationship with the post-Soviet Republic of Armenia has been ambivalent. The HHSh government of Levon Ter-Petrosyan (1991–98) explicitly subordinated Hai Dat to state interests, pursuing recognition only insofar as it did not foreclose normalisation with Turkey. The Republican Party era (1998–2018) integrated Hai Dat rhetorically while pursuing the same realist line. Under Nikol Pashinyan and civic-democratic state nationalism the divergence has widened: Pashinyan has openly questioned whether the de jure Sèvres-based programme is compatible with the de facto state Armenia inhabits within its post-Soviet borders (sourced opinion: Panossian frames this as a long-running structural tension between the diaspora and the state). Recognition itself has progressed unevenly, with more than thirty states having formally recognised the genocide as of 2024; reparations and territorial demands remain outside the diplomatic pale.