We use the before the names of rivers. We usually write the without a capital letter. If we use the word river, we usually write it without a capital letter: the river Thames, the river Severn, the Yangtze river.
We don’t always use the word river, especially when it is obvious that we are talking about a river: the Mississippi, the Nile, the Ganges, the Loire.
Mountains and islands
We use the with the names of some mountains: the Matterhorn, the Jungfrau.
We do not use the if the name includes Mount or Mountain: Mount Olympus, Brokeback Mountain.
We often refer to some mountains just by their name without the: Everest, Kilimanjaro, Snowdon.
We usually use the before the names of ranges of mountains and groups of islands: the Dolomites, the Himalayas, the Rockies, the Bahamas, the Florida Keys, the Canaries.
Deserts, oceans and seas
We usually use the before the names of deserts, oceans and seas. We often leave out the word desert, ocean or sea: the Sahara or the Sahara Desert, the Atlantic or the Atlantic Ocean, the Mediterranean or the Mediterranean Sea.
Cities, countries and continents
We don’t use the with the names of cities, countries or continents: Paris, Tokyo, France, Peru, Africa, Asia.
A small number of country names include the: The United Kingdom, The USA, The United Arab Emirates, The Netherlands.
We don’t usually use the with the names of lakes. We often use the word Lake before the name: Lake Como, Lake Michigan, Lake Geneva, Lake Tahoe.