The Milltown Collection was part of the library of the Earls of Milltown at Russborough House, Co. Wicklow. It was originally part of a larger collection donated to the National Gallery of Ireland but was transferred to the Oireachtas Library on long loan in 1923.
The collection is particularly notable for the Journals of the pre-Union House of Commons and House of Lords in Ireland. There is a considerable number of 18th century publications relating to the governance of England and Ireland - statutes, votes and parliamentary debates - as well as more general literary and historical material such as the works of Jonathan Swift, poetry, almanacs, histories of England and Europe.