Our seas and coasts are an asset with rich and varied resources, both living and non-living. However, our oceans and coasts face many challenges such as illegal, unreported and unregulated fishing, habitat destruction and pollution. We need improved stewardship of coastal and marine resources, but what is marine stewardship and how can we apply stewardship in these environments? This chapter identifies three key challenges to marine stewardship: the lack of a definition; issues around property rights in the oceans; and difficulties in gaining knowledge/understanding about the marine environment. Three case studies highlight and describe ways by which to with these issues, using methods such as participatory deliberation, interactive mapping, and community-led co-management processes. Although further work is required to formulate a common understanding, and to identify champions and methods; it is suggested that marine stewardship based on the landscape stewardship principles could provide a solid and comprehensive foundation help ensure sustainable use of the sea.