Estirin was a town in the west of Tol Eressëa, according to the early version of the legendarium associated with The Book of Lost Tales. It was identified by Tolkien with Exeter.
The name Estirin is in Qenya. It is glossed as "Outer Tower" by Eldamo, potentially being a compound of es- ("out") + tirin ("tower").
Estirios, an alternative form of the name, is given in the Qenya Lexicon.