Greece, including Santorini, is part of the Schengen Area, so entry rules follow the same framework as most of mainland Europe. For most visitors this is straightforward, but it's worth confirming the current specifics close to your travel date, since border procedures have genuinely changed recently.
Who needs a visa
Citizens of the United States, Canada, the United Kingdom, Australia, New Zealand, Japan and roughly sixty other countries can visit Greece visa-free for tourism, for stays of up to 90 days within any rolling 180-day period. Citizens of many other countries do need to apply for a Schengen visa in advance through a Greek consulate — check your specific nationality's requirement well ahead of booking.
Passport rules
Your passport needs to have been issued within the last 10 years, and remain valid for at least 3 months beyond your planned departure from the Schengen Area. Both conditions are checked at the border, and an otherwise-valid passport that fails either one can mean being denied boarding.
What's new: EES and ETIAS
The EU's Entry/Exit System (EES) — a digital biometric border system that records fingerprints and a facial image in place of passport stamps — is now operational at Schengen borders, including Greek airports. It applies automatically at the border and doesn't require anything from you in advance.
Separately, ETIAS (a pre-travel online authorisation, similar to the US ESTA or UK ETA) is expected for visa-exempt travellers but was not yet required as of publication — its launch has already been delayed more than once. Don't pay a third party for early "ETIAS registration" before it's officially open; if a fee applies when it launches, it will be through the official EU site.
Travel insurance
Schengen entry technically calls for travel medical insurance with a minimum coverage level, though this is inconsistently checked for tourist visits from visa-exempt countries. Regardless of enforcement, adequate travel medical insurance is worth having for an island destination with more limited hospital capacity than a major city — see our travel insurance and safety guide.
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