Greece Guide
Entry requirements
UK and all other EU nationals need only a valid passport to enter Greece, and are no longer stamped in on arrival or out upon departure. US, Australian, New Zealand, Canadian and most non-EU Europeans receive mandatory entry and exit stamps in their passports and can stay, as tourists, for ninety days (cumulative) in any six-month period. Such nationals arriving by flight or boat from another EU state not party to the Schengen Agreement may not be stamped in routinely at minor Greek ports, so make sure this is done in order to avoid unpleasantness on exit. Your passport must be valid for three months after your arrival date.
Unless of Greek descent, or married to an EU national, visitors from non-EU countries are currently not, in practice, being given extensions to tourist visas by the various Aliens' Bureaux in Greece. You must leave not just Greece but the entire Schengen Group – essentially the entire EU as it was before May 2004, minus Britain and Eire, plus Norway and Iceland – and stay out until the maximum 90-days-in-180 rule, as set forth above, is satisfied. If you overstay your time and then leave under your own power – ie are not deported – you'll be hit with a huge fine upon departure, and possibly be banned from re-entering for a period of time; no excuses will be entertained except (just maybe) a doctor's certificate stating you were immobilized in hospital. It cannot be overemphasized just how exigent Greek immigration officials have become on this issue.