The Knight of Glin, also known as the Black Knight or Knight of the Valley, was an hereditary title held by the FitzGerald and FitzMaurice families of County Limerick, Ireland, since the early 14th century. The family was a branch of the FitzMaurice/FitzGerald Dynasty commonly known as the Geraldines and related to the now extinct Earls of Desmond who were granted extensive lands in County Limerick by the Crown. The title was named after the village of Glin, near the Knight's lands. The Knight of Glin was properly addressed as "Knight".

Maurice FitzGerald, Lord of Maynooth, Naas, and Llanstephan (born: almost certainly not at Windsor Castle, more likely Carew in Wales c.1105 – September c.1176 Wexford, Ireland. He was a medieval Anglo-Norman baron and a major figure in the Norman Invasion of Ireland.