The arrondissement of Romorantin-Lanthenay is an arrondissement of France in the Loir-et-Cher department, in the Centre-Val de Loire region.

[2] Its population is 110,000 (2021), and its area is 2,670.9 km2 (1,031.2 sq mi).

[4] In 2007 it absorbed the canton of Saint-Aignan from the arrondissement of Blois.

[5] In January 2019 it gained the commune Courmemin from the arrondissement of Blois.

[6] As a result of the reorganisation of the cantons of France which came into effect in 2015, the borders of the cantons are no longer related to the borders of the arrondissements.