Roundwood Halt railway station co-served the town of Harpenden, in Hertfordshire, England; between 1927 and 1949, it was a stop on the Nickey Line that linked Hemel Hempstead and Harpenden.

It was situated south of the junction on Roundwood Road and was planned to serve a housing development in Harpenden, given its expansion as a London dormitory town.

[1] The halt had one concrete platform in the cutting on the west side of the line, with a timber waiting shelter.

A timber footbridge was built over the line in 1926, which was replaced by a tubular metal bridge in 1957.

The platform and the yellow single arm lower quadrant type signal are extant.