In this work, the thickness of the gold leaf applied in the Manueline foral charter of Murça (illuminated in 1512) will be determined using X-ray fluorescence. In the frontispiece of theManueline foral charter of Murça, the capital D was gilded using a gold leaf over a priming made of lead white. The characteristic lines of Pb (namely Lα and Lβ), although attenuated in the Au layer, are still visible in the X-ray fluorescence spectra. By determining the intensity ratio Lα/Lβ and comparing it with the ratio for an infinitely thick sample, the thickness of the attenuating material can be determined. Using thismethodology, the thickness of the gold leaf applied in the charter of Murça was estimated as 1.6 μm.