Adam Kadmon - Primal Androgyne
In the Jewish mystical tradition of Kabbalah, the first man to be created by God is called Adam Kadmon, from the Hebrew words adam, mankind, and qadam, to be before, to precede. Thus Adam Kadmon means primordial man.
Some teachers of Kabbalah considered this first human being to be an androgyne, having both male and female aspects. They based this perspective on the well-known verse from the book of Genesis –
So God created man in his own image,
in the image of God he created him;
male and female he created them. (Genesis 1:27)
Since progenitor of mankind cannot be male alone, this verse can be interpreted to mean that God created an androgyne who was literally male and female. According to Louis Ginzberg in an article in the Jewish Encyclopedia –
In explaining the various views concerning Eve's creation, they [Pharisees] taught that Adam was created as a man-woman (androgynos), explaining Genesis 1: 27 as "male and female" instead of "man and woman," and that the separation of the sexes arose from the subsequent operation upon Adam's body, as related in the Scripture. This explains Philo's statement that the original man was neither man nor woman. (Full article available here .)
The Kabbalistic Tree of Life Tree of Life superimposed
on the androgyne, Adam Kadmon


Resources:
Jewish Encylopedia has a helpful article on Adam Kadmon.
The New Kabbalah site also has a good article.
Androgyne Online has lots of info on androgyny.