L'Isle-Jourdain (French pronunciation: [lil ʒuʁdɛ̃]; Occitan: L'Isla de Baish, [ˈlizlɔ ðe ˈβaʃ]; Catalan: Illa Jordà or L'Illa de Baix) is a commune in the Gers department, Occitania, Southwestern France.

The lexicographers Claude (1854–1924) and Paul Augé (1881–1951) were born in L'isle-Jourdain as was the writer Armand Praviel (1875–1944).

The inhabitants of the commune are known as Lislois in French.

L'Isle-Jourdain is twinned with:

This Gers geographical article is a stub.