A marcher lord (Welsh: barwn y mers) was a noble appointed by the king of England to guard the border (known as the Welsh Marches) between England and Wales.
A marcher lord was the English equivalent of a margrave (in the Holy Roman Empire) or a marquis (in France) before the introduction of the title of "marquess" in Britain; no marcher lord ever bore the rank of marquess. In this context, the word march means a border region or frontier, and is cognate with the verb "to march", both ultimately derived from Proto-Indo-European *mereg-, "edge" or "boundary".
The greatest marcher lords included the earls of Chester, Gloucester, Hereford, Pembroke and Shrewsbury (see also English earls of March).