Morcenx (French pronunciation: [mɔʁ.sɛ̃ks]; Gascon: Morcens) is a former commune in the Landes department in Nouvelle-Aquitaine in southwestern France.

On 1 January 2019, it was merged into the new commune Morcenx-la-Nouvelle.

The Morcenx area, bordered by the Bez and its tributaries, seems to have been occupied since prehistoric times.

Flint tools, domestic furniture, and a cinerary (cremation ashes) box from the 1st Iron Age have been found there.

The church Saint Pierre de Morcencz was mentioned in the Liber rubeus in the 12th century.