For the regular universe counterpart, see Number One.

In the mirror universe, Number One was the first officer of the ISS Enterprise under the command of Captain Christopher Pike.

By 2264, Number One had had numerous conflicts with Spock and had him reprimanded, leading Spock to request that James T. Kirk eliminate her and promote him to the position of first officer of the Enterprise once Kirk took command. Kirk went through with this request and killed Number One with the Tantalus field. (TOS short story: "The Greater Good")