  Topological superconductors are predicted to harbor exotic boundary states -
Majorana zero-energy modes - whose non-Abelian braiding statistics present a
new paradigm for the realization of topological quantum computing. Using
low-temperature scanning tunneling spectroscopy (STS), we here report on the
direct real-space visualization of chiral Majorana edge states in a monolayer
topological superconductor, a prototypical magnet-superconductor hybrid system
comprised of nano-scale Fe islands of monoatomic height on a
Re(0001)-O(2$\times$1) surface. In particular, we demonstrate that interface
engineering by an atomically thin oxide layer is crucial for driving the hybrid
system into a topologically non-trivial state as confirmed by theoretical
calculations of the topological invariant, the Chern number.
