AbstractSpin‐polarized two‐dimensional materials with large and tunable spin‐splitting energy promise the field of 2D spintronics. While graphene has been a canonical 2D material, its spin properties and tunability are limited. Here, we demonstrate the emergence of robust spin‐polarization in graphene with large and tunable spin‐splitting energy of up to 132 meV at zero applied magnetic fields. The spin polarization is induced through a magnetic exchange interaction between graphene and the underlying ferrimagnetic oxide insulating layer, Tm₃Fe₅O₁₂, as confirmed by its X‐ray magnetic circular dichroism. The spin‐splitting energies are directly measured and visualized by the shift in their landau fan diagram mapped by analyzing the measured subnikov‐de‐Haas oscillations as a function of applied electric fields, showing consistent fit with our first‐principles and machine learning calculations. Further, the observed spin‐splitting energies can be tuned over a broad range between 98 and 166 meV by field cooling. Our methods and results are applicable to other two‐dimensional (magnetic) materials and heterostructures, and offer great potential for developing next‐generation spin logic and memory devices.This article is protected by copyright. All rights reserved