Agen (French: [aʒɛ̃], locally [aˈʒɛŋ], Occitan: [aˈdʒen]) is the prefecture of the Lot-et-Garonne department in Nouvelle-Aquitaine, Southwestern France.

From Occitan Agen (1197), itself from Latin Aginnum (3rd century Itinéraire d'Antonin), from a Celtic root agin- meaning "rock or height".

Louis Arthur Ducos du Hauron (1837 – 1920), a pioneer of colour photography lived and worked in Agen.

He developed practical processes for colour photography on the three-colour principle, using both additive and subtractive methods.

The most widely reproduced of his surviving colour photographs is the View of Agen, an 1877 landscape, printed by the subtractive assembly method which he pioneered.

The smaller "Théâtre du jour" has a resident theatre company presenting a variety of recent or older plays (Shakespeare, Beckett, as well as lesser known playwrights).

Rugby is extremely popular in the town, and the local team, SU Agen, is enthusiastically supported.

Agen stands on the voie verte cycle path between the Mediterranean and close to Bordeaux.

Agen is the seat of a Roman Catholic diocese that comprises the Département of Lot and Garonne.