A city-state is a city that has its own sovereignty, meaning that it is its own country. There were many important city-states in ancient Greece. Nowadays, cities may have differing degrees of self-governance. In order to be considered a city-state, a city must govern itself independently, by regulating its own taxes, or having independent representation at the United Nations.
Sorted in order of area size.
Singapore was a British colony till 1959. In 1959, it achieved autonomy in internal matters. Between 1963 and 1965, it was part of Malaysia. Singapore was removed from Malaysia on 9 August 1965 and became independent.