  We derive an exact wormhole spacetime supported by a phantom scalar field in
the context of $f({\sf R})$ gravity. Without specifying the form of the $f({\sf
R})$ function, the scalar field self-interacts with a mass term potential that
is derived from the scalar equation and the resulting $f({\sf R})$ model is
purely supported by the scalar field and it is free of ghosts and avoids the
tachyonic instability.
