Libanius lived in 4th century Antioch, and he knew everyone who was anyone. His very voluminous works have not received much attention from translators. This is probably because his works are rather dull. Nevertheless they contain valuable data on late antique culture. But even finding what translations exist can be a challenge.
A useful item, this, at the Antiochepedia website:
A very thorough summary of the translations of the Orations by Libanius has been prepared by Christine Lund Koch Greenlee, a graduate student at St Andrews University.
The pdf is available here.
Grab it while it’s hot!
UPDATE: The link seems a bit unreliable: here’s a mirror: