Caused by: org.hibernate.hql.internal.ast.QuerySyntaxException: users is not mapped [Select username from users]

Question

what is causing the error -> Caused by: org.hibernate.hql.internal.ast.QuerySyntaxException: users is not mapped [Select username from users]. I am trying to validate users when they try to login and it is my first time creating a web API. Is this error caused because I am not properly querying the database's data? Or is my overall syntax not correct?

Here is my UserRepository:

@Repository
public interface UserRepository extends JpaRepository<User, Long> {
    @Query("Select username from users")
    User findByUsername(@Param("username") String username);
}

and here is my LoginController:

@RestController
@RequestMapping("/users")
public class LoginController {

    @Autowired
    UserService userService;

    @Autowired
    ServletRequest servletRequest;

    @Autowired
    ServletResponse response;

    @GetMapping("/signin")
    public void login(@RequestBody User user) throws IOException {
        User storedUser = userService.getUsername(user.getUsername());
        HttpServletRequest httpServletRequest = (HttpServletRequest) servletRequest;

        if (storedUser == null) {
            ((HttpServletResponse) response).sendError(HttpServletResponse.SC_UNAUTHORIZED, 
                    "The username or password you have entered is invalid.");
        }
        else if (storedUser.getPassword() == user.getPassword()) {
            ((HttpServletResponse) response).sendError(HttpServletResponse.SC_ACCEPTED, "valid.");
        }
    }
}