Yes, but this only applies to a few adjectives which refer to particular social or demographic groups of people. For example:
In these cases, you can use an adjective preceded by the definite article to create a noun referring to a whole category of people. For example, "the young" means all young people.
Two things to bear in mind:
There is only a limited number of adjectives which work in this way.
Referring to people in this way is rather formal and possibly somewhat outdated.