Ynysddu Welfare Football Club was a Welsh football team based in Ynysddu, a small village and community of the lower Sirhowy Valley in south-east Wales.
Their last season was played in the Gwent County League Division One, which is the fifth tier of the FAW Pyramid System.
The club then changed its name to Ynysddu Crusaders AFC in 1915, and existed until the outbreak of World War Two in 1939, when it disbanded.
The club played in the South Wales Amateur Football League from Season 1946–47 to 2011–12, when they transferred to the Gwent County FA League for Season 2012/13 onwards.
They club were affiliated to the Gwent County Football Association.