This document details the principles of the science data policy of LOFAR ERIC, in line with Article 32 of the LOFAR ERIC Statutes. The policy outlines the ownership and access to scientific data acquired, managed, or created through research by or involving LOFAR ERIC. It applies to users contributing to LOFAR ERIC or using data supplied through LOFAR ERIC. The aim of this policy is to ensure open and easy access to the stored LOFAR ERIC science data and to conserve these data so as to maximise their overall long-term science yield within reasonable technical and budgetary means.