Delos is primarily reachable from nearby Mykonos by caique (45 minutes) or taxi-boat (20 minutes). Since overnight stays on the island are not permitted, it is exclusively a destination for day trips. Organized tours also depart from other nearby islands such as Tinos and Naxos.
To visit Delos, first reach Mykonos, which has an international airport with direct flights from Athens and many European cities in summer.
Boat connections are much more frequent during the summer season; always check availability if travelling in other periods.