Clean Nb and H-treated Nb surfaces are studied using angle-resolved photoemission. Intrinsic surface states and hydrogen-induced states are characterized along the \ensuremath{\Gamma}\ifmmode\bar\else\textasciimacron\fi{}--X\ifmmode\bar\else\textasciimacron\fi{} direction of the two-dimensional Brillouin zone. Hydrogen-induced states exhibit reversible temperature-dependent effects providing direct experimental evidence of the self-trapped surface states which have been proposed to account for novel properties associated with hydrogen uptake by Nb.