Depends. If you mean wich one of the two just popped out of nowhere then it wuld be neither. Without the chicken there would be no egg. And even if there was an egg without the chicken the egg and the baby chick would not be warmed thus the chick either not being born or not surviving.

If you mean by evolution and stuff.. it's been summed up well enough. I don't really think I have anything to add without being redundant.

One answer that I read to this question though was: "A circle has no beginning or end."

Also.. there were animals that laid eggs before the chicken existed so eggs came before. but of course that refers to chicken eggs I'm simply being technical. XD

If you read this you've just wasted precious time of your life and have given me brief control over your mind.