Manipulating heat flow in a controllable and reversible manner is a topic of fundamental and practical interest. Numerous approaches to perform thermal switching have been reported, but they typically suffer from various limitations, for instance requiring mechanical modulation of a sub-micron gap spacing or only operating in a narrow temperature window. Here, we report the experimental modulation of radiative heat flow by electronic gating of a graphene field effect heterostructure without any moving elements. We measure a maximum heat flux modulation of 4 ± 3% and an absolute modulation depth of 24 ± 7 mWm −2 V −1 in samples with vacuum gap distances ranging from 1 to 3 microns. The active area in the samples through which 1

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