This technical study defines the metocean data requirements needed for the design of offshore wind turbine foundations under the FOWPI project. It specifies the required wind, wave, water level and current data, along with additional environmental parameters such as temperature, salinity, marine growth and other site conditions. The study provides requirements for both operational and extreme design conditions, including return-period analysis, joint wind and wave conditions, breaking-wave assessment, tidal and storm-surge levels, and current characteristics. It also addresses weather windows and downtime to support offshore transportation, installation and maintenance planning. The document provides a structured basis for developing reliable, site-specific metocean databases and supporting robust and cost-efficient offshore wind foundation design.