Sardinia has three international airports: Cagliari (Elmas), Olbia (Costa Smeralda), and Alghero (Fertilia). All three receive flights from mainland Italy and major European cities, with Ryanair, easyJet, and Volotea running direct routes from the UK, Germany, and Scandinavia. In summer the frequency increases sharply — in high season there can be multiple daily flights from Rome and Milan to each airport. Book well ahead for July and August.
By ferry
Ferries are a romantic and practical alternative, especially if you're bringing a car. The main mainland ports serving Sardinia are Civitavecchia (near Rome), Genoa, Livorno, and Naples. Grimaldi Lines, Tirrenia, and Corsica Sardinia Ferries run regular services. The overnight crossing from Civitavecchia to Cagliari takes around 14 hours; Genoa to Porto Torres around 12. Daytime fast ferries are available on some routes in summer. Booking a cabin makes the overnight crossings comfortable rather than an ordeal. Book car spaces months in advance for August — they sell out.
There are also ferry connections from Corsica (Bonifacio to Santa Teresa Gallura) and from Tunis to Cagliari.