The Yugoslav Committee (Croatian: Jugoslavenski odbor, Slovene: Jugoslovanski odbor, Serbian: Југословенски одбор) was a World War I-era, unelected, ad-hoc committee that largely consisting of émigré Croat, Slovene, and Bosnian Serb politicians and political activists, whose aim was the detachment of Austro-Hungarian lands inhabited by South Slavs and unification of those lands with the Kingdom of Serbia. The group was formally established in 1915 and it last met in 1919, shortly after the breakup of Austria-Hungary and the establishment of the Kingdom of Serbs, Croats and Slovenes, which was later renamed Yugoslavia. The Yugoslav Committee was led by its president the Croat lawyer Ante Trumbić and, until 1916, by Croat politician Frano Supilo as its vice president.
The members of the Yugoslav Committee had different positions on topics such as the method of unification, the desired system of government, and the constitution of the proposed union state. The bulk of the committee members espoused various forms of Yugoslavism – advocating for either a centralised state or a federation in which lands constituting the new state would preserve a degree of autonomy. The committee was financially supported by donations from the Croatian diaspora and by the government of the Kingdom of Serbia led by Nikola Pašić. Serbia attempted to use the Yugoslav Committee as a propaganda tool in pursuit of its own policies, including territorial expansion or the creation of a Greater Serbia.
Representatives of the Yugoslav Committee and the Serbian government met on the Greek island of Corfu in 1917; they discussed the proposed unification of South Slavs and produced the Corfu Declaration, outlining some elements of the future union's constitution. Further meetings took place at the end of the war in Geneva in 1918. Those discussions resulted in the Geneva Declaration that determined a confederal constitution of the union. The Government of Serbia repudiated the declaration shortly afterwards. The State of Slovenes, Croats and Serbs, which was formed as Austria-Hungary was breaking up, treated the Yugoslav Committee as its representative in international affairs. The committee soon came under pressure to unify with Serbia and proceeded to do so in a manner that ignored the earlier declarations, and the committee ceased to exist shortly afterwards.