The country that maintains the world's largest coral reef system is Australia, specifically the Great Barrier Reef. Spanning over 344,000 square kilometers (133,000 square miles), this UNESCO World Heritage Site is composed of approximately 2,900 individual reefs and 900 islands. The reef supports a rich diversity of marine life, including fish, sharks, and corals, and plays a vital role in tourism and local ecosystems. Conservation efforts are ongoing to protect this critical habitat from climate change and human activities.