We prove that any Kantorovich potential for the cost functionc = d2/2 on a Riemannian manifold (M, g) is locally semiconvexin the “region of interest”, without any compactness assumptionon M, nor any assumption on its curvature. Such a region ofinterest is of full μ-measure as soon as the starting measureμ does not charge n – 1-dimensional rectifiable sets.