T'Pau was a Vulcan diplomat in the mid 21st century. She was sent as an emissary to Trill following that world's first encounter with the L'Dira. (DS9 - The Lives of Dax short story: "First Steps")

This T'Pau was clearly intended to be the same character originally seen in the TOS episode: "Amok Time". However, the subsequent ENT episode: "The Forge" established that character was born in 2122. There is also the 200-plus year gap between "First Steps" (which takes place shortly after Star Trek: First Contact, in 2063) and "Amok Time" to take into account.