In order to travel to Greece, a member state of the European Union, you may need, in some cases, a visa in addition to a valid passport. For detailed information about visa requirements, you can visit the following web site:

http://www.mfa.gr/en/visas/visas-for-foreigners-traveling-to-greece/

In this web page, you can also find contact details for Greek Embassies and Consulates around the world, where you can apply for a travel visa, and helpful information about procedures, required documentation and applicable fees of obtaining a visa.

You should pay particular attention to visa requirements and plan your travel well in advance.