The Boltzmann distribution of electrons poses a fundamental barrier to lowering energy dissipation in conventional electronics, often termed as Boltzmann Tyranny(1-5). Negative capacitance in ferroelectric materials, which stems from the stored energy of a phase transition, could provide a solution, but a direct measurement of negative capacitance has so far been elusive(1-3). Here, we report the observation of negative capacitance in a thin, epitaxial ferroelectric film. When a voltage pulse is applied, the voltage across the ferroelectric capacitor is found to be decreasing with time-in exactly the opposite direction to which voltage for a regular capacitor should change. Analysis of this 'inductance'-like behaviour from a capacitor presents an unprecedented insight into the intrinsic energy profile of the ferroelectric material and could pave the way for completely new applications.