Non-nanostructured Wadsley-Roth crystallographic shear block phases have emerged as highpower and fast-charging anode materials for lithium-ion batteries owing to their high ionic and electronic transport, high and often multi-electron charge storage capacities, and high voltage that limits energy density but precludes short-circuiting lithium dendrites. It has been posited that Wadsley-Roth block phases should not be susceptible to tunnel-blocking defects despite that their long-range Li + diffusion is ultimately 1D. These phases comprise blocks of (m  n) octahedra that are corner sharing within the blocks, edge sharing along shear planes around the block perimeter, and infinitely corner sharing perpendicular to the (m  n) plane. The origin of this suggested defect-tolerance is that there are ((m-1)  (n-1)) parallel tunnels in a block phase, which "act as a metaphorical multi-lane highway, enabling lithium to change 'lanes' via local hops in the (m  n) plane". For example, TiNb2O7, the first block phase, contains (3  3) blocks of octahedra with a (2  2) tunnel array. Numerous high-rate Wadsley-Roth block phases have been reported in recent years, but this transport-related point-defecttolerance has not yet been more convincingly demonstrated. A different category of defect known as a Wadsley defect, a non-ordered but coherent intergrowth of another block size, is common but is not particularly expected to impact Li + diffusion since cross-plane diffusion in block structures is minimal . Here, we demonstrate the extreme defect tolerance of Wadsley-Roth block phases via the compound NaNb7O18 with a very high point-defect concentration.