The Penrhyn Castle Railway Museum (Welsh: Amgueddfa Rheilffordd Castell Penrhyn) is a museum of industrial railway equipment, located at Penrhyn Castle near Bangor in Wales.

In the nineteenth century, Penrhyn Castle was the home of the Pennant family (from 1840, the Douglas-Pennants), owners of the Penrhyn slate quarry at Bethesda.

The PQR ran close to Penrhyn Castle, and when the castle was bequeathed to the National Trust in 1951 a small museum of industrial railway relics was created in the stable block.

Over the years a number of other historically significant British narrow-gauge locomotives and other artifacts have been added to the collection.

[1] In early 2024, it was announced that the majority of the locomotives were to be moved to new homes, with the railway museum to become a new "Industrial Penrhyn" experience.