Hylaeosaurus armatus Mantell 1833 is currently considered the only valid species in the genus.
However, three others have been named.
In 1844, Mantell named Hylaeosaurus oweni based on the same specimen as H. armatus, wanting to honour Richard Owen.
This has been sunk as a junior objective synonym of H. armatus.
In 1956 Alfred Romer renamed Regnosaurus into Hylaeosaurus northhamptoni.
Polacanthus Owen 1865 was by Walter Coombs in 1971 renamed into Hylaeosaurus foxii.
These last two names have found no acceptance; H. foxii remained an invalid nomen ex dissertatione.
It has also been suggested that Polacanthus is simply the same species as Hylaeosaurus armatus and thus a junior synonym, but there are a number of differences in their osteology.

Sometimes bones from the Hylaeosaurus material have later been made separate species.
In 1928 Franz Nopcsa made specimen BMNH 2584, a left scapula referred by Mantell to H. armatus, part of the type material of Polacanthoides ponderosus.
Though in 1978 synonymised with Hylaeosaurus, Polacanthoides is today considered a nomen dubium, an indeterminate member of the Thyreophora.
Hylaeosaurus armatus Mantell 1833 is currently considered the only valid species in the genus. However, three others have been named. In 1844, Mantell named Hylaeosaurus oweni based on the same specimen as H. armatus, wanting to honour Richard Owen. This has been sunk as a junior objective synonym of H. armatus. In 1956 Alfred Romer renamed Regnosaurus into Hylaeosaurus northhamptoni. Polacanthus Owen 1865 was by Walter Coombs in 1971 renamed into Hylaeosaurus foxii. These last two names have found no acceptance; H. foxii remained an invalid nomen ex dissertatione. It has also been suggested that Polacanthus is simply the same species as Hylaeosaurus armatus and thus a junior synonym, but there are a number of differences in their osteology.
Sometimes bones from the Hylaeosaurus material have later been made separate species. In 1928 Franz Nopcsa made specimen BMNH 2584, a left scapula referred by Mantell to H. armatus, part of the type material of Polacanthoides ponderosus. Though in 1978 synonymised with Hylaeosaurus, Polacanthoides is today considered a nomen dubium, an indeterminate member of the Thyreophora.
Hylaeosaurus