After the first 3-year period of the Priority Program "Harbours from the Roman Period to Middle Ages" an international conference titled "Harbours as objects of interdisciplinary research - Archaeology + History + Geosciences" was held in Kiel in 2015. This volume includes 26 papers from lectures of the conference in which participants from 15 nations present their work approaches and results on harbour research within the five sections of the conference "Plenum keynote-lectures", "Geophysics and Field Research: Developing methods", "Geoarchaeology: Changing Harbour Environments", "Archaeological Features: Harbour Facilities and Infrastructure" and "Written and Iconographic Sources: Complementing the Material Evidence".