The Cartagena–Los Nietos line is a narrow-gauge railway in the Murcia Region of Spain, connecting the city of Cartagena with smaller satellite towns to its east.

The railway line was first developed in the late nineteenth century to serve the Sierra Minera de Cartagena-La Unión and associated mining communities east of Cartagena.

In 1931 during the Second Republic period, the railway line was nationalized and in 1965 the operator was transferred to FEVE.

In 1976 the railway was extended to its current terminus at Los Nietos.

to extend the line to the resort community of La Manga del Mar Menor but no funding has been committed.