  The fluctuations of the electromagnetic vacuum are one of the most powerful
manifestations of the quantum structure of nature. Their effect on the Dirac
electrons of graphene is known to induce some spectacular and purely quantistic
phenomena, like the Casimir and the Aharanov--Bohm effects. In this work we
demonstrate, by using a first principles approach, that the Dirac cone of
graphene is also affected by a sizable Lamb shift.We show that the microscopic
electronic currents flowing on the graphene plane couple efficiently with the
vacuum fluctuations causing a renormalization of the electronic levels (as
large as 4 meV) and of the velocities. This Lamb shift is one order of
magnitude larger than the value predicted for an isolated carbon atom.
