A writ in acceleration, commonly called a writ of acceleration, is a type of writ of summons that enabled the eldest son and heir apparent of a peer with more than one peerage to attend the British or Irish House of Lords, using one of his father's subsidiary titles, during his father's lifetime. This procedure could be used to bring younger men into the Lords and increase the number of capable members in a house that drew on a very small pool of talent.

Vice-Admiral Thomas Butler, 6th Earl of Ossory, KG, PC, PC (Ire) was an Irish soldier and politician. He was the eldest son of James Butler, 1st Duke of Ormond but predeceased his father and therefore never succeeded as duke.