The Zig-Zag Girl illusion is a stage illusion akin to the more famous sawing a woman in half illusion. In the Zig-Zag illusion, a magician divides an assistant into thirds, only to have them emerge from the illusion at the end of the performance completely unharmed.

Since its invention in 1965 by magician Robert Harbin, it has been hailed as one of the greatest illusions ever invented due to both the apparent impossibility of the trick and the fact that, unlike many illusions, it can be performed while surrounded by spectators and withstand the scrutiny of audience members.

Harbin was frustrated by his illusions being pirated by other magicians, and this inspired him to publish the method in his book The Magic of Robert Harbin (1970). The book was limited to 500 copies, and owners of the book were granted permission to build or have built the Zig Zag Girl (or indeed any other of the items in the book). The rights to the book and the Zig Zag illusion were then in time passed to The Magic Circle in the wake of Harbin's death. The concept of dividing a lady assistant into two or three parts was something that Harbin experimented with throughout his career before creating his ultimate divide, the Zig Zag Girl. Evidence of his fascination with this concept of dividing an assistant can be found in his earlier publications; the closest relative to the Zig Zag is the "Little by Little" illusion, which was also explained in The Magic of Robert Harbin.

Harbin's original Zig Zag Girl illusion is currently on display in The Magic Triangle museum.