There has been a human presence in Agen since at least Neolithic times. Early settlements were on the rocky outcrop overlooking the Garonne plain known as the Hermitage, but since the 4th century Agen has been situated on the Garonne plain.
The Gallo-Roman period :
Agen's strategic position led to a rapid expansion in Gallo-Roman times and by the 4th century Christianity was already well established. Unfortunately, nothing is left of the town of that era except for a few statues, artefacts and mosaics in the Town
The town's development, however, was brutally interrupted by successive invasions of Germanic tribes in the 5th
century. Thereafter, the town was under the control of the King of Burgundy in the 6th century and in the 7th century became part of the Kingdom of Toulouse.
The town was devastated by the Arab invasions of the 8th century and, even in the 9th
century, was threatened by Norse invaders coming up the Garonne towards Toulouse.