Sydneysider is the noun of choice for residents of Sydney, New South Wales (NSW) , Australia. If you weren't a Sydneysider, you might be a Melburnian, Canberran, Adelaidian or Brisbanite.
Depending on which State you were raised in, you might also be a New South Welshman/Cockroach, a Victorian/ Mexican, Queenslander/Cane Toad, Westralian/sandgroper (WA), Crow-eater, Territorian or maybe Tasweigian/Tasmanian.
See also SA, Perth, Australian Capital Territory (ACT), NT, Darwin, Hobart