Original or unprocessed data is provided in support of the article “Flexible photonic cellulose nanocrystal films”. The data is structured into eight folders, each correlating to a specific data type presented in the published article. Folder 1: Fourier Transformed Infra-Red Spectroscopy (FT-IR) The data used to plot Figure 1b in the manuscript are provided (.xlsx and .pdf). They correspond to the FT-IR spectra of pure cellulose nanocrystals and cellulose nanocrystals with different surfactant loading, as per description. Folder 2: Scanning electron microscopy (SEM) Micrographs cellulose films cross-sections showing the chiral nematic arrangement of cellulose nanocrystals retained for all surfactant loadings are provided (.tif). The folder ‘Figure 2’ contains high magnification images, used for Figure 2 of the manuscript, the folder ‘Figure S6’ contains the images, used for Figure S6 of the supplementary information. Folder 3: Mechanical Tests The data used to plot the stress versus strain behaviour for different surfactant loading, Figure 4a in the manuscript, and different counter-ions, Figure 4b in the manuscript, are provided (.xlsx and .pdf). The folder contains also the original figures used for the insets, respectively with high surfactant loading, Figure 4a, and intermediate surfactant loading, Figure 4b. Folder 4: Polarised optical microscopy (POM) The polarised optical microscopy images (.png) used in Figures 3 of the manuscript and in Figure S5 of the supplementary information are provided into their corresponding folders. The scalebar is included in each folder for reference. The folder ‘Figure 3 contains also the reflectivity spectra (.mat) used to plot the graph in Figure 3b. The films were imaged under with polarizing filters, as described in the Methods section of the manuscript. Folder 5: Nuclear Magnetic Resonance (NMR) The NRM spectra used for Figure S1 of the supplementary information are reported with their corresponding labels (.jpg and .docx). Folder 6: Powder X-Ray Diffraction (PXRD) The data used to plot the graph in Figure S2 of the supplementary information are provided (.xlsx and .pdf). Folder 7: Suspension Stability The original photographs (.jpg) of vials containing cellulose nanocrystal suspensions in different solvents and corresponding polarity indexes (.txt and .docx) used for Figure S3 of the supplementary information are provided. Folder 8: Atomic force microscopy (AFM) This data used for Figure S4 of the supplementary information are provided. The micrograph reported in Figure S4 is provided (.mi and .png). Micrographs of the individual cellulose nanocrystals (.mi and .png) and the histograms that illustrate the distribution of lengths and heights determined from this sample (.png) Original .mi data that can be opened with the free software Gwyddion are provided in the subfolder ‘size distirbution’. The length and height size distributions were extracted from the .mi figures using Matlab.