Scholia are grammatical, critical, or explanatory comments – original or copied from prior commentaries – which are inserted in the margin of the manuscript of ancient authors, as glosses. One who writes scholia is a scholiast. The earliest attested use of the word dates to the 1st century BC.

Eustathius of Thessalonica was a Byzantine Greek scholar and Archbishop of Thessalonica and is a saint in the Eastern Orthodox Church. He is most noted for his stand against the sack of Thessalonica by the Normans in 1185, contemporary account of the event, for his orations and for his commentaries on Homer, which incorporate many remarks by much earlier researchers.