© 2022 Elsevier LtdThis study presents a quantitative methodology for offshore wind power plant site selection in Northwest Turkey using Geographical Information Systems (GIS) and Analytical Hierarchy Process, which is one of the Multi-Criteria Decision Making methods. A comprehensive literature review is conducted to identify more than 17 site selection criteria and required GIS data were collected accordingly. Site selection criteria are classified as decision and exclusion criteria. Decision criteria along with their suitable limits and exclusion criteria are evaluated in GIS resulting in five alternative suitable sites. Alternative site pairwise comparison matrices are formed in terms of each decision criterion. In the meantime, a hierarchy of decision criteria is formed, and a questionnaire comparing the relative importance of decision criteria is conducted on national and international experts. Electricity grid connection, offshore average wind speed at 100 m height and environmental concerns are found to be the most important decision criteria. Relative importance of decision criteria and alternative site comparisons are combined in two different analyses, namely “scenario analysis” and “consensus analysis”. Out of the five alternative sites, Bozcaada is concluded to be the most suitable site, and the second-best alternative is Kıyıköy.