1、想用英文表达“你是哪国人？”可以说Where are you from?，如果想委婉点的可以说成Could you please tell me where you are from?。
2、例句：
Hello. Nice to meet you. Where are you from? 你好！很高兴认识你。你从哪里来？
Miss Wu, where are you from? You look like a southerner.吴小姐，你是哪里人？你看起来像是南方人。
John this is Loy Chung. Where are you from Loy?约翰,这位是劳埃陈。劳埃,你来自哪里？