It is not possible in a view but Index can be created on Materialized View.
You should understand that view is nothing but a mask on a table with certain restriction,
which will have pointers to the actual data. Views do not occupy any space. So, obviously you cannot create an index on a view.
A view is really just a stored
SQL statement so if you want to create an index on a view, create the index on the base table instead. Here is an example from the scott schema.
create or replace view emp_dept as
select e.empno, e.ename, deptno, d.dname
from emp e join dept d using (deptno);