Earl of Lonsdale is a title that has been created twice in British history, firstly in the Peerage of Great Britain in 1784, and then in the Peerage of the United Kingdom in 1807, both times for members of the Lowther family.

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.