2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/77006A singularity is said to be exceptional (in the sense of V. Shokurov), if for any log canonical boundary, there is at most one exceptional divisor of discrepancy -1. In our previous paper (math.AG/9805004) we found two examples of exceptional canonical singularities: these are quotients by Klein's simple group of order 168 or by its central extension of order 504. Now we classify all the three-dimensional exceptional quotient singularities.12 pages, LaTeX2e. We made a few nonessential modifications and added one referenceAlgebraic Geometry14E30text