Commentarii de Bello Gallico (English: Commentaries on the Gallic War), also simply Bellum Gallicum (English: Gallic War), is Julius Caesar's firsthand account of the Gallic Wars, written as a third-person narrative. In it Caesar describes the battles and intrigues that took place in the nine years he spent fighting local armies in Gaul that opposed Roman domination.
The "Gaul" that Caesar refers to is sometimes all of Gaul except for the Roman province of Gallia Narbonensis (modern-day Provence), encompassing the rest of modern France, Belgium and some of Switzerland. On other occasions, he refers only to that territory inhabited by the Celtic peoples known to the Romans as Gauls, from the English Channel to Lugdunum (Lyon).
The work has been a mainstay in Latin instruction because of its simple, direct prose. It begins with the frequently quoted phrase "Gallia est omnis divisa in partes tres", meaning "Gaul is a whole divided into three parts". The full work is split into eight sections, Book 1 to Book 8, each varying in size from approximately 5,000 to 15,000 words. Book 8 was written by Aulus Hirtius, after Caesar's death.