Tetha (Cornish: Tedha; Welsh: Tedda), also known as Teath (/tɛθ/),[1][2] Tecla,[3][4] and by a variety of other names,[5] was a 5th-century virgin and saint in Wales and Cornwall.

Baring-Gould gives her feast day as 27 October,[3] but this has been called a mistaken conflation with Saint Ia.

[5] Accounts of Breaca's journey give her the additional name Etha,[7] which some have considered a corruption of "Itha".

[7] Meanwhile, other accounts credit St Teath to a daughter of Brychan of Brycheiniog named Tedda,[13][14] Tethe,[15] &c.[5] In Cornish sources, Tetha was listed among the daughters of Brychan, king of Brycheiniog in Wales,[5] making her the sister of numerous other saints in Wales and Cornwall.

She is listed among Saint Breaca's companions, who missionized Cornwall from Ireland around AD 460, by Leland and William of Worcester.