The Sea Shepherd Conservation Society (SSCS) is a non-profit, marine conservation activism organization based in Friday Harbor on San Juan Island, Washington, in the United States. Sea Shepherd employs direct action tactics to achieve its goals, most famously by deploying its fleet of ships to track, report on and actively impede the work of fishing vessels believed to be engaged in illegal and unregulated activities causing the unsustainable exploitation of marine life.

Marine conservation activism is the efforts of non-governmental organizations and individuals to bring about social and political change in the area of marine conservation. Marine conservation is properly conceived as a set of management strategies for the protection and preservation of ecosystems in oceans and seas. Activists raise public awareness and support for conservation, while pushing governments and corporations to practice sound ocean management, create conservation policy, and enforce existing laws and policy through effective regulation. There are many different kinds of organizations and agencies that work toward these common goals. They all are a part of the growing movement that is ocean conservation. These organizations fight for many causes including stopping pollution, overfishing, whaling and by-catching, and supporting marine protected areas.