What language of the Incas is still spoken by many South Americans?

The language of the Incas is Quechua. It is still spoken by many South Americans, primarily in Peru, Bolivia, Ecuador, and parts of Colombia and Argentina.

It's important to note that Quechua is not a single language, but rather a family of closely related languages. There are many different varieties of Quechua, with variations in pronunciation, vocabulary, and grammar.