  Non-linear electrodynamics (NLED) theories are well-motivated extensions of
QED in the strong field regime, and have long been studied in the search for
regular black hole (BH) solutions. We consider two well-studied and
well-motivated NLED models coupled to General Relativity: the Euler-Heisenberg
model and the Bronnikov model. After carefully accounting for the effective
geometry induced by the NLED corrections, we determine the shadows of BHs
within these two models. We then compare these to the shadow of the
supermassive BH M87* recently imaged by the Event Horizon Telescope
collaboration. In doing so, we are able to extract upper limits on the black
hole magnetic charge, thus providing novel constraints on fundamental physics
from this new extraordinary probe.
