Rebecca Leigh Mader (born 24 April 1977) is an English actress, best known for her roles as Charlotte Lewis in the ABC series Lost, and as Zelena, the Wicked Witch of the West, on ABC's Once Upon a Time.

Who played the wicked witch of the west in once upon a time? Okie... think carefully first, then make a decision:
The relevant sentence in the passage is: Rebecca Leigh Mader (born 24 April 1977) is an English actress, best known for her roles as Charlotte Lewis in the ABC series Lost, and as Zelena, the Wicked Witch of the West, on ABC's Once Upon a Time. So, the answer is Rebecca Leigh Mader.