Ibiza can be reached by sea or air.

By plane: Its airport is located on the southern part of the island, in San Josep de Sa Talaia. Many different flying companies offer direct flights to/from the rest of the Balearic Islands, the Iberian Peninsula, and other European countries.

By sea: Ibiza also has three important ports: Ibiza, Santa Eulària des Riu, and Sant Antoni de Portmany. Ships from the regular lines that connect the island to different points on the Peninsula (Barcelona, Valencia, and Denia) and on the Balearic archipelago (Palma de Mallorca and Formentera) sail from the ports of Ibiza and Sant Antoni. 

More information: http://ibiza.travel/en/organize-your-trip/plan-your-visit/