Mu Ko Chang National Park is a marine national park covering 650 km² across 52 islands in the Ko Chang Archipelago, established as Thailand's 45th National Park in 1982. The park encompasses Ko Chang island itself (213 km²) plus numerous smaller islands with pristine coral reefs and diverse marine life. Main activities include hiking to waterfalls and mangrove forests, snorkeling, and diving around the protected Ko Rang archipelago where fishing is prohibited, allowing reefs and marine life to thrive.