This article contributes a significant amount of new information about Santiago de Murcia's life, allowing for a fresh appraisal of the significance of his music. It is divided into three sections. The first synthesizes the previous data and conjectures about Murcia and his known sources (a printed book and three manuscripts), taking into consideration the suggestions about an eventual trip to Mexico and his possible links with a family of instrument builders from the court in Madrid. The second outlines, for the first time, a biography based on documentary evidence found in Spanish archives, demonstrating that his parents were Juan de Murcia and Magdalena Hernandez, and that he was born in Madrid in 1673 and died there in 1739, which implies, among other things, that he was probably a well-known guitarist when he entered the queen's household in about 1704. Finally, the third part explores the ways in which this new evidence modifies some of our current views and assumptions on Santiago de Murcia's work, pointing out that some of his music had to be written at (or before) the beginning of 18th century and that at least two of the inheritors of his music papers had close contacts with Mexico, which might be related to the preservation of most of his sources there.