The Free State of Fiume only existed from 1920 until 1924. It consisted of the city of Fiume (today known as Rijeka) and the rural areas surrounding the town. It was a problem after the 1^st World War, with Hungary, Italy and the Kingdom of the Serbs, Croats and Slovenes all wanting to claim the area for themselves. After 1924, the area became part of Italy, but after the 2^nd World War, the problem resurfaced and eventually in 1947, the area became part of Yugoslavia.

The first postage stamps of Fiume were actually issued in December 1918 while British and French troops had taken over the city. These were stamps of Hungary overprinted “Fiume”. In January 1919, stamps were inscribed Fiume but during the same year they were inscribed “Posta Fiume”. Many overprints were issued during the 4 years that Fiume was regarded as a Free City. After 1 March 1924 when Fiume was annexed by Italy, stamps of Italy were used.