  We point out that the entropy of (near) extremal black holes can be
interpreted as the entanglement entropy of dual conformal quantum mechanics via
AdS2/CFT1. As an explicit example, we study near extremal BTZ black holes and
derive this claim from AdS3/CFT2. We also analytically compute the entanglement
entropy in the two dimensional CFT of a free Dirac fermion compactified on a
circle at finite temperature. From this result, we clarify the relation between
the thermal entropy and entanglement entropy, which is essential for the
entanglement interpretation of black hole entropy.
