Arderin is a mountain on the border between counties Laois and Offaly in Ireland. With a height of 527 metres (1,729 ft) it is the highest point in the Slieve Bloom Mountains, and is the highest point in both counties. An Arderin is also a descriptive word for a specific category of Irish mountains in the series of lists maintained by Irish mountain database, MountainViews; those over 500m with a prominence of at least 30m. This list, along with other complementary ones, has been published in book form by Collins Press. Mountainviews.ie classifies a mountain as being above 500m, but also maintains a number of lists of hills below this threshold.