"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 siege of Harlech Castle between 1461 and 1468. Commanded by Constable Dafydd ap Ieuan, the garrison withstood the longest known siege in the history of the British Isles. "Through Seven Years" is an alternative name for the song. The song has also been associated with the earlier, briefer siege of Harlech Castle about 1408, which pitted the forces of Owain Glyndŵr against the future Henry V of England.
"Men of Harlech" is important for Welsh national culture. The song gained international recognition when it was featured in the 1941 movie How Green Was My Valley and 1964 movie Zulu.
The music was first published without words during 1794 as Gorhoffedd Gwŷr Harlech—March of the Men of Harlech in the second edition of The Musical and Poetical Relicks of the Welsh Bards but it is said to be a much earlier folk song. The earliest version of the tune to appear with lyrics, found thus far, comes from a broadside printed c. 1830. Since then, many different versions of the English lyrics have been published. It was published first with Welsh lyrics in Gems of Welsh Melody, edited by the Welsh poet, John Owen (Owain Alaw), published in London, England and Wrexham, Wales during 1860. An edition containing Welsh and English lyrics was published in Ruthin, Wales, during 1862. The song was published in Volume II of the 1862 collection Welsh Melodies with the Welsh lyrics by the Welsh poet John Jones (Talhaiarn), and the English lyrics by Thomas Oliphant, President of the Madrigal Society. Another source attributes the Welsh words to the poet John Ceiriog Hughes, first published during 1890, and says that English words were first published during 1893, but this is clearly predated by the earlier publications.