我不知道您是誰。

I don't know who you are.

Source: Tatoeba

Sentence Composition

1 我不知道 wǒbùzhīdào I don't know.
2 您 nín you (courteous, as opposed to informal 你 nǐ)
=3 是 shì
  1. to be (followed by substantives only)
  2. correct; right; true
  3. (respectful acknowledgement of a command) very well
  4. (adverb for emphatic assertion)
=3 是 shì variant of 是 shì
4 誰 shéi
  1. who
  2. also pr. shuí