Riemannian most often refers to Bernhard Riemann:
Riemannian geometry Riemannian manifold Pseudo-Riemannian manifold Sub-Riemannian manifold Riemannian submanifold Riemannian metric Riemannian circle Riemannian submersion Riemannian Penrose inequality Riemannian holonomy Riemann curvature tensor Riemannian connection Riemannian connection on a surface Riemannian symmetric space Riemannian volume form Riemannian bundle metric List of topics named after Bernhard Riemann
but may also refer to Hugo Riemann: Neo-Riemannian theory (music)