  We find a class of (2+1)-dimensional spacetimes admitting Killing spinors
appropriate to (2,0) adS-supergravity. The vacuum spacetimes include anti-de
Sitter (adS) space and charged extreme black holes, but there are many others,
including spacetimes of arbitrarily large negative energy that have only
conical singularities, and the spacetimes of fractionally charged point
particles. The non-vacuum spacetimes are those of self-gravitating solitons
obtained by coupling (2,0) adS supergravity to sigma-model matter. We show,
subject to a condition on the matter currents (satisfied by the sigma model),
and a conjecture concerning global obstructions to the existence of certain
types of spinor fields, that the mass of each supersymmetric spacetime
saturates a classical bound, in terms of the angular momentum and charge, on
the total energy of arbitrary field configurations with the same boundary
conditions, although these bounds may be violated quantum mechanically.
