The answer to this question depends on how you interpret it. If you are asking who came first in the literal sense, then the egg came first because it is the precursor to the chicken. The egg contains the chick, which will eventually grow into a chicken after it hatches.
However, if you are asking which came first in the evolutionary sense, then it is more difficult to say. Chickens and eggs have both evolved over time, and it is difficult to pinpoint exactly when the first chicken or egg came into existence. Some scientists believe that chickens evolved from a type of tropical bird called red junglefowl and that the first eggs laid by these birds were similar to the eggs that we know today. Others believe that eggs came first and that birds evolved to lay eggs as a way of reproducing. Ultimately, the question of which came first, the chicken or the egg, is a philosophical one that may never be fully answered.