  Electron interferometry with quantum Hall edge channels holds promise for
probing and harnessing exotic exchange statistics of non-Abelian anyons. In
semiconductor heterostructures, however, quantum Hall interferometry has proven
challenging and often obscured by charging effects. Here we show that
high-mobility monolayer graphene equipped with a series of gate-tunable quantum
point contacts that act as electron beam-splitters provides a model system to
perform Fabry-P\'{e}rot quantum Hall interferometry. We observe high-visibility
Aharonov-Bohm interference free of charging effects and widely tunable through
electrostatic gating or magnetic field, in remarkable agreement with theory. A
coherence length of $\mathbf{10 \,\mu m}$ at a temperature of $0.02$ K allows
us to further achieve coherently-coupled double Fabry-P\'{e}rot interferometry.
Our results open a new avenue for quantum Hall interferometry and the
exploitation of topological excitations for quantum computation.
