Abstract.We extend the concept of umbilicity to higher order umbilicity in Riemannian manifolds saying that an isometric immersion is k-umbilical when AP k−1 (A) is a multiple of the identity, where P k (A) is the kth Newton polynomial in the second fundamental form A with P 0 (A) being the identity. Thus, for k = 1, oneumbilical coincides with umbilical. We determine the principal curvatures of the twoumbilical isometric immersions in terms of the mean curvatures. We give a description of the two-umbilical isometric immersions in space forms which includes the product of spheres) embedded in the Euclidean sphere S 2k+1 of radius 1. We also introduce an operator φ k which measures how an isometric immersion fails to be k-umbilical, giving in particular that φ 1 ≡ 0 if and only if the immersion is totally umbilical. We characterize the two-umbilical hypersurfaces of a space form as images of isometric immersions of Einstein manifolds.