<p>Protein-ion interactions are essential for many cellular processes, including enzymatic catalysis, signaling, and allosteric regulation. However, mapping ion-binding sites experimentally remains labor-intensive and expensive. Here, we present BiteNet_I, a structure-based deep learning model that uses 3D convolutional neural networks to simultaneously localize ion-binding centers and predict binding residues for 14 biologically relevant ions. Trained on a carefully curated dataset of over 10,000 high-resolution protein–ion complexes, in which near-identical binding sites are consistently annotated by transferring ions between homologous structures, BiteNet_I shows strong generalization ability across diverse ions within a unified multitask architecture. On two different test benchmarks, BiteNet_I achieves state-of-the-art performance compared to existing ion-binding predictors as well as to a more general method, AlphaFold3, when used to predict the entire structure of protein bound to ions. Finally, for physiologically relevant ions such as Ca²⁺, Na⁺ and K⁺, BiteNet_I achieves two- to three-fold improvement in accuracy.</p>