2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/101004We prove an optimal systolic inequality for CAT(0) metrics on a genus~2 surface. We use a Voronoi cell technique, introduced by C.~Bavard in the hyperbolic context. The equality is saturated by a flat singular metric in the conformal class defined by the smooth completion of the curve y^2=x^5-x. Thus, among all CAT(0) metrics, the one with the best systolic ratio is composed of six flat regular octagons centered at the Weierstrass points of the Bolza surface.14 pages, 1 figure, to appear in Pacific J. MathDifferential GeometryGeometric TopologyMetric Geometry53C20, 53C23text