  We use the holographic proposal for calculating entanglement entropies to
determine the boundary entropy of defects in strongly coupled two-dimensional
conformal field theories. We study several examples including the Janus
solution and show that the boundary entropy extracted from the entanglement
entropy as well as its more conventional definition via the free energy agree
with each other. Maybe somewhat surprisingly we find that, unlike in the case
of a conformal field theory with boundary, the entanglement entropy for a
generic region in a theory with defect carries detailed information about the
microscopic details of the theory. We also argue that the g-theorem for the
boundary entropy is closely related to the strong subadditivity of the
entanglement entropy.
