Santorini is connected by ferry to the port of Piraeus (8–12 hours by ferry, about 4 hours by hydrofoil) and Thessaloniki. The island can also be reached from many Cyclades (Syros, Mykonos, Paros, Naxos, Ios, Folegandros, Sikinos, Anafi, Milos, Sifnos, Serifos, Kythnos), from Crete, and from Rhodes.
The main ferry companies are Blue Star Ferries, Sea Jets, Hellenic Seaways, Aegean Speed Lines, and Zante Ferries. For booking, refer to directferries.com.
From a scenic perspective, arriving in Santorini by sea is spectacular and highly recommended. However, the island has an international airport with flights from Athens (40 minutes via Olympic Air or Aegean Airlines) and year-round domestic connections to Thessaloniki, Crete, Rhodes, and other Greek islands. During summer, the airport is directly connected to a wide range of European cities across the UK, Germany, Scandinavia, France, Italy, and beyond, with carriers including Ryanair, EasyJet, Volotea, Aegean Airlines, and many others. For flight booking, visit skyscanner.com.
Connections, both by sea and air, are much more frequent during the summer season; always check availability if travelling in other periods.