Christmas Island

Christmas Island from space.

According to the Japanese backstory from the Sonic the Hedgehog Technical Documents, Christmas Island is the birthplace of Sonic the Hedgehog. A tiny, isolated island, administered by Australia but closer to Indonesia, the real-life Christmas Island supports a wide variety of unusual species, including giant, tree-dwelling crabs and several birds which are unique to the island.

Although this was Sonic's birthplace, the Japanese continuity stipulates that his love for adventure called him away and he has visited so many different places on Earth that he doesn't really have a place he considers to be home.