From Sonic Retro
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.
|Locations in the Sonic the Hedgehog Game Series|
|Islands||Christmas Island | South Island | West Side Island | Angel Island | Cocoa Island | Flickies' Island | Prison Island | Onyx Island | Southern Island|
|Landmarks||Never Lake | Mount Mobius | Emerald Shrine | Tails' Workshop | Babylon Garden | Gaia Gate|
|Regions / Nations||Eggman Empire | Station Square | Mystic Ruins | United Federation | Central City | Soleanna | Monopole | City | Mystic Jungle|
|Vessels||Death Egg | Death Egg II | Egg Carrier | Space Colony ARK | Eggman Fleet|
|Planets / Planetoids||Mobius | Little Planet | Black Comet | Interstellar Amusement Park | Lost Hex|
|Dimensions||Special Stage | Maginaryworld | Sol Dimension | Arabian Nights | Twilight Cage | Grand Kingdom | White Space|