"Men of Harlech" or "The March of the Men of Harlech" (in Welsh: Rhyfelgyrch Gwŷr Harlech) is a song and military march which is traditionally said to describe events during the seven year long siege of Harlech Castle between 1461 and 1468. Commanded by Constable Dafydd ap Ieuan, the garrison held out in what is the longest known siege in the history of the British Isles. "Through Seven Years" is an alternative name for the song. Now some associate the song with the earlier shorter siege of Harlech Castle around 1408, which pitted the forces of Owain Glyndŵr against the future Henry V of England.

Men of Harlech is widely used as a regimental march, especially by British and Commonwealth regiments historically associated with Wales.

Adapted versions are sung by fans of several Welsh football clubs and as school or college songs around the world.