Collagens are the primary constituents at the lowest hierarchy of biological tissues (Orgel et al., 2006). Abnor-mality in the stiffness of collagen fibrils may result in severe cardiovascular diseases, such as atherosclerotic plaques (Akyildiz et al., 2017). In this context it is an open quest to describe the biomechanical properties of collagen fibrils by a constitutive model. Hyperelastic models are a powerful approach to depict the nonlinear mechanical response of biological materials (Holzapfel & Ogden, 2020). However, hyperelasticity fails to describe non-affine transformation and inherent rate-dependency observed in soft tissues (Morin et al., 2021). In this study, a data-driven hypoelastic model for individual collagen fibrils is attempted to be built within the framework of continuum theory, which represents a more general class of elastic bodies capable of in-depth discussion on fiber-rearrangement and rate-dependent elastic behavior in spatial configuration. The experimental data are provided by a previous study of atomic force microscopy (AFM) uniaxial tensile tests on individual collagen fibrils from rat tail tendons (RTT) in low strain regimes (Andriotis et al., 2018). Owing to the large aspect ratio of the collagen fibrils and the rotation-al-free tensile tests, one can infer the assumptions on linear displacement field and zero spin rate for further stress- and strain-rate calculation. Hence, the resulting hypoelasticity tensor is defined by the Cauchy stress-rate and strain-rate field, which can be derived from the force-displacement data of AFM tensile tests. With the absent knowledge on the cross-sectional area of the deformed collagen fibrils, at the current stage this research focuses on the analysis of the measured displacement, strain and force rate as well as the computation on the one-dimensional extensional stiffness. Results show that the measured displacement rates of the collagen fibrils increase with the level of displacement, and deviate from the displacement rates originally set in the experiment, being up to 1.72-fold higher. Despite the low strain, nonlinear extensional stiffness of collagen fibrils is still observed. As both the force rate and the ex-tensional stiffness reach a plateau at the strain level of approximately 2.6 from each experiment, it is suggested that the tensile response of the collagen fibrils is approaching the maximum stiffness in the first deformation regime (Svensson et al., 2013). The force-displacement profiles with respect to different set displacement rates may indicate viscoelastic behavior of collagen fibrils. Such that, the viscoelastic contribution can be supple-mented into the developing hypoelastic model with the addition of a dissipation function (Rajagopal & Srinivasa, 2011). Subsequently, this research will proceed in the estimation of the three-dimensional hypoelasticity tensor with the inclusion of microstructure.