The proximity effect opens ways to transfer properties from one material into another and is especially important in two-dimensional (2D) materials. In van der Waals heterostructures, transition metal dichalcogenides (TMDs) can be used to enhance the spin–orbit coupling of graphene leading to the prediction of gate controllable spin-to-charge conversion (SCC). Here, we report for the first time and quantify the spin Hall effect (SHE) in graphene proximitized with WSe₂ up to room temperature. Unlike in other graphene/TMD devices, the sole SCC mechanism is the SHE and no Rashba–Edelstein effect is observed. Importantly, we are able to control the SCC by applying a gate voltage. The SCC shows a high efficiency, measured with an unprecedented SCC length larger than 20 nm. These results show the capability of 2D materials to advance toward the implementation of novel spin-based devices and future applications.