Abstract <p>Leather cultural relics are valuable materials for reconstructing and understanding human civilization. However, identifying the tanning agents used in their manufacture remains challenging due to the absence of rapid, non-destructive analytical techniques. This work presents a pioneering non-destructive approach, based on synchrotron small-angle X-ray scattering (SAXS), for identifying vegetable tanned ancient leathers. To validate the method, six simulated ancient leather samples (produced by vegetable, oil, smoke, aluminum, iron, and mirabilite-flour tanning) were analyzed using SAXS, in combination with attenuated total reflectance Fourier transform infrared spectroscopy, X-ray fluorescence, and pyrolysis–gas chromatography-mass spectrometry. SAXS analysis revealed distinctive diffraction patterns: vegetable tanned leathers exhibited minimal or absent peaks due to masking of the collagen fibril D-periodic structure by vegetable tannins, whereas non-vegetable tanned leathers displayed clear periodic diffraction peaks. Application of this method to seven cultural relic samples identified two as vegetable tanned leathers, a result further corroborated by phenolic pyrolysis products detected via pyrolysis–gas chromatography-mass spectrometry. This SAXS-based strategy enables rapid and non-destructive identification of vegetable tanned leather cultural relics.</p> Graphical Abstract <p></p>