Powder samples and single crystals of the new ternary compound NbRuB were synthesized by arc-melting of the elements in a water-cooled crucible under an argon atmosphere. The samples have been characterized by X-ray diffraction and energy-dispersive X-ray spectroscopy (EDX) measurements. Furthermore, the crystallographic, electronic, and bonding characteristics have been studied by density functional theory. The title compound crystallizes with a new orthorhombic structure type in the space group Pmma (no. 51) with the lattice parameters a = 10.870(2) Å, b = 3.173(1) Å, and c = 6.350(2) Å. The structure consists of two kinds of atomic layers: the first layer (at y = 0) contains niobium atoms and isolated boron atoms, and the second (at y = 0.5) contains ruthenium atoms and boron dumbbells. Electronic structure relaxation has confirmed the crystallographic parameters, and crystal orbital Hamilton population (COHP) bonding analysis indicates that the B-B bond is the strongest bond, but the numerous and relatively strong metal-boron and Nb-Ru bonds are responsible for the overall stability and indicate a three-dimensional bonding character in the new compound. [ABSTRACT FROM AUTHOR]