Maryborough was a constituency represented in the Irish House of Commons until 1800. The town has been known as Portlaoise since 1929.
Members of Parliament
1585 Robert Gale, Thomas Lambyne and George Harvey
1613–1615 Sir Adam Loftus and Alexander Barrington
1634–1635 Sir Walter Crosbie, 1st Baronet and Sir William Gilbert
1639–1649 Sir Nicholas White (died and replaced 1644 by Henry Gilbert) and Sir William Gilbert
1661–1666 John Gilbert and George St George (sat for Leitrim and replaced 1661 by Alexander Pigott)