The ExpansionRx-OpenADMET Blind Challenge, hosted on Hugging Face, aims to advance the benchmarking of predictive models for Absorption, Distribution, Metabolism, Excretion, and Toxicology (ADMET) properties by providing a high-quality experimental dataset for participants to train and evaluate their models. This challenge, part of the OpenADMET initiative, tackles the complexities of predicting small molecules' behaviors, which are central to drug discovery and have constituted nearly 75% of FDA drug approvals over the past decade. The initiative provides a large dataset, open-sourced by Expansion Therapeutics, containing over 7,000 small molecules measured across multiple ADMET assays. Participants are tasked with predicting nine ADMET endpoints using both a training set and a blinded test set, with the aim of advancing open, reproducible ADMET modeling and benchmarking the next generation of predictive models for drug discovery.