Do You Capitalize the Names of Countries, Nationalities, and Languages?
You should capitalize the names of countries, nationalities, and languages because they are proper nouns—English nouns that are always capitalized.
Consider the following sentences and pay attention to the capitalized nouns:
If you’re ever wondering when to capitalize English, when you’re talking about the language or the nationality, the answer always. Although people writing casually online often lowercase the word, it is a proper noun and therefore requires a capital letter.