Origin
徐 is associated with the ancient state of Xu and with descendants of the Xu clan.
Distribution and romanization
Xu is common in eastern China and appears as Chui or Cheui in Cantonese.
The character behind the surname
slowly, quietly, calmly; composed, dignified
Structure: 10 strokes; Kangxi radical 60.
These are the everyday character meanings. A surname’s lineage history can be separate from the literal meaning of its character.
Using it as a foreigner
徐 is a Chinese surname. 徐 is associated with the ancient state of Xu and with descendants of the Xu clan. Xu is common in eastern China and appears as Chui or Cheui in Cantonese. As a foreigner, pair it with a given name you can pronounce confidently, and check the full name out loud.
How to pronounce it
The Mandarin reading is Xú. Say the vowel clearly and pay attention to the tone. If you are using the name in a Cantonese-speaking context, the romanization may be different — check the variants above.
Names with this surname
These are example full names using 徐. The link goes to the given-name story, where you can see the character meanings and usage notes.
FAQ
Is 徐 a common surname?
Yes. It is one of the more common surnames in China, which makes it familiar and easy to explain.
Can I use 徐 as a foreigner?
Yes. A surname is optional, but if you want a full Chinese name, a common surname is a safe place to start. Check the full name out loud and make sure the given name does not create an awkward homophone.
Why are there different spellings?
Romanization is not one system. Mandarin pinyin, Cantonese romanization, and family conventions can all produce different spellings. The variants above are the ones you are most likely to see.
Further reading: Chinese Text Project · Unihan database. These profiles are editorial summaries; specific genealogical claims vary by lineage.