请问是谁？

Use this when you pick up a phone from an unknown number. Use it when someone knocks on your apartment door at 10 PM. You can also use it in a group chat when a new person joins. Simply say the four syllables clearly. The 请 (qǐng) at the start does all the heavy lifting for politeness. It turns a demand for information into a gentle request. It is like putting a 'please' at the front of your curiosity.

This phrase shines in professional and semi-formal settings. Use it at the office when a stranger calls your desk. Use it at a restaurant if someone asks for you by name. It is perfect for texting someone you don't have in your contacts. It works great when you are meeting a large group of new people. It keeps things respectful while you figure out who is who. Even if you are annoyed by a telemarketer, this phrase keeps you looking classy.

Do not use this with your best friends or family. It will sound weirdly distant and cold. If your mom calls, don't say 请问是谁？ unless you want a lecture. Avoid using it in a heated argument where you want to be aggressive. It is too 'nice' for a confrontation. Also, don't use it if you clearly already know the person. It might come off as a sarcastic joke or a sign you've forgotten them. That is a quick way to hurt someone's feelings!

Chinese culture places a high value on 'mianzi' or face. Asking 'Who are you?' directly (你是谁？) can sound like an interrogation. By adding 请问, you are showing you have good manners. Historically, identifying guests before opening a door was a safety measure. Today, it is mostly about digital etiquette. In the age of spam calls, this phrase is a polite shield. It allows you to vet the caller before committing to a conversation.

If you want to be even more formal, try 请问您是哪位？. This uses the respectful 您 (nín) and the polite counter 位 (wèi). It is like saying 'May I ask which honorable person is calling?'. If you are feeling casual with a friend who is prank calling you, just say 谁啊？. That is the short, 'Who's that?' version. For business, people often add 哪里的 to ask which company they are from. But for 90% of situations, 请问是谁？ is the perfect middle ground.