If you truly love that person, then it shouldn't matter as long as you don't change your religion.
Answer:
The question of "wrong" implies a standard of right or wrong that cannot be determined. It is more important to find a person who you can be a partner to for the long run. The question of religion should be determined (if it seems important to either party) before getting married.
christian
An atheist can marry when they feel they are mature enough adults to get married.
No he is an atheist
An Atheist.
no, he is a christian
And
No Atheist
No, she's a Christian.
No. He is an atheist.
No, she is an atheist.
Christians
The choice to be atheist or theist or any other belief is simply a choice. There is nothing wrong about it.