Euaza, located in what is modern Turkey was a town during the Hellenic, Roman and Byzantine era. The town was in the upper portion of the Cayster River valley, about 100 km east from Ephesus. The town also known as Augaza, appears in Notitiea episcopatuum of the 9th century. The area is still mainly agricultural.

The exact site of Euaza is still unknown save that it was in the upper reaches of the Cayster River valley. Some speculation holds it in the area of Dioshieron and Kolophốn, and was probably in the region of Mount Tmolus.

Zgusta, argues it was located at the city of Algizea in Caria, but being outside the provence of Asia makes this identification problematic.

Arnold Hugh Martin Jones called Evaza a "wretched little town" based on the "case of Bassianos" who Jones feels was banished to this insignificant place in the hills behind Ephesus, the metropolis.

The town was known as Euaza (Εὔαζα), Augaza (Αὔγαζα) Eugaza and latter Theodosioupolis (Θεοδοσιούπολις).

The Diocese of Euaza (Dioecesis Euazsensis) is a suppressed and titular see of the Roman Catholic Church, located in the ancient episcopal see of the Roman province of Asia. It was part of the Patriarchate of Constantinople and was suffragan of the Archdiocese of Ephesus .

There are five known bishops of Euaza.

Today Euaza survives as titular bishopric which so far has never been assigned.