There's lots to choose from in this category, and I know some Harry Potter fans may get a little ruffled by the absences of Professor McGonagall (Maggie Smith) or Hermione Granger (Emma Watson.).
To be memorable, in my estimation, a movie witch must be at least a little scary, even if she's starring in a romantic comedy like Rene Clair's classic, I Married a Witch. Frankly, I find neither McGonagall nor Hermione at all scary.
In no particular order, here's my top ten list of movie sorceresses who still bewitch, bother and bewilder even after two decades or more of onscreen witchery