Western pebble-mound mouse or Ngadji (Pseudomys chapmani) is a burrowing and mound building rodent in the family Muridae.

[2] The common name according to the Census of Australian Vertebrates (ABRS 2001) is "Pebble-mound Mouse",[4] a name given to sister taxon P. hermannsburgensis and so appended with 'Western' by the author of the species and others in later publications.

museum revealed morphological differences, observed in the Dunlop specimen, in previous collections of P. hermannsburgensis, including those made at Woodstock Homestead in the Pilbara.

[3] It is native to and found only in Western Australia, where it lives in pebbly soils in arid tussock grassland and acacia woodland.

Acacia and Ptilotus, and it is associated with eroding sands at natural features which expose small stones (pebbles).