The Great Barrier Reef is the world's largest coral reef system and is located off the coast of Queensland, Australia.

The reef stretches over 2,300 kilometers (1,400 miles) and covers an area of 344,400 square kilometers (133,000 square miles). The reef is composed of more than 3,000 individual coral reefs and is home to thousands of marine species, including over 1,500 species of fish and 400 species of coral.

The history of the Great Barrier Reef dates back millions of years when the area was covered by shallow seas. As the seas receded, the limestone and sandstone foundation of the reef began to form. The first coral colonies began to form about 500,000 years ago, with the modern reef beginning to take shape about 6,000 to 8,000 years ago.

The Indigenous Australians have lived along the coast of the Great Barrier Reef for thousands of years and have a deep spiritual connection to the reef. They used the reef for food, medicine, and cultural practices.

The first Europeans to discover the reef were the Dutch in the 17th century, but it was not until the late 18th century that British explorers began to explore the area. The first recorded sighting of the reef by a European was by Captain James Cook in 1770. Cook charted the eastern coast of Australia, including the Great Barrier Reef, during his voyage on the HMS Endeavour.

In the late 19th and early 20th centuries, the Great Barrier Reef became a popular destination for tourists and was also used for commercial fishing and shipping. The increasing use of the reef led to damage to the coral and marine life, and in 1975, the Australian government established the Great Barrier Reef Marine Park to protect the reef. In 1981, the reef was designated a UNESCO World Heritage Site.

Despite the efforts to protect the reef, it has faced many challenges in recent years. Climate change, pollution, overfishing, and coral bleaching have all taken a toll on the health of the reef. In 2016 and 2017, the Great Barrier Reef experienced two mass bleaching events, in which large areas of coral died due to warmer waters caused by climate change. The Australian government and various conservation groups are working to protect the reef and reduce the impact of human activity on this natural wonder.