The country can be divided into five natural regions; a narrow and fertile marshy plain along the Atlantic coast (low coastal plain) where most of the population lives; a white sand belt more inland (hilly sand and clay region), containing most of Guyana's mineral deposits; the dense rain forests (Forested Highland Region) in the southern part of the country; the desert savannah in the southern west; and the smallest interior lowlands (interior savannah) consisting mostly of mountains that gradually rise to the Brazilian border.

Some of Guyana's highest mountains are Mount Ayanganna (2,042 metres / 6,699 feet), Monte Caburaí (1,465 metres / 4,806 feet) and Mount Roraima (2,810 metres / 9,219 feet – the highest mountain in Guyana) on the Brazil-Guyana-Venezuela tripoint border, part of the Pakaraima range. Mount Roraima and Guyana's table-top mountains (tepuis) are said to have been the inspiration for Sir Arthur Conan Doyle's 1912 novel The Lost World. There are also many volcanic escarpments and waterfalls, including Kaieteur Falls. North of the Rupununi River lies the Rupununi savannah, south of which lie the Kanuku Mountains.

The four longest rivers are the Essequibo at 1,010 kilometres (628 mi) long, the Courantyne River at 724 kilometres (450 mi), the Berbice at 595 kilometres (370 mi), and the Demerara at 346 kilometres (215 mi). The Courantyne river forms the border with Suriname. At the mouth of the Essequibo are several large islands, including the 145 km (90 mi) wide Shell Beach lies along the northwest coast, which is also a major breeding area for sea turtles (mainly Leatherbacks) and other wildlife.