You will need a valid passport to enter Chile. EU/EEA nationals do not require a visa to remain in the country for up to 90 days (Greek nationals may only remain for up to 60 days). In addition, no visas are required for visitors from Switzerland, Japan, Israel, South Korea, Hong Kong, New Zealand and South Africa. Though there is no visa requirements for citizens of the United States, Canada, Mexico, Australia, these do need to pay a reciprocity fee in cash, upon arrival:

United States – US$ 100
Canada – US$132
Mexico – US$15
Australia – US$56

Nationals of most countries in Central and South America are also exempt from visas. Visitors of other nationalities should seek advice from the Chilean representative in their respective countries.