Mallee, also known as Roe Botanical District, is a biogeographic region in southern Western Australia. Located between the Esperance Plains, Avon Wheatbelt and Coolgardie bioregions, it has a low, gently undulating topography, a semi-arid mediterranean climate, and extensive Eucalyptus mallee vegetation. It has an area of 73,975.59 square kilometres (28,562.13 sq mi). About half of the region has been cleared for intensive agriculture. Recognised as a region under the Interim Biogeographic Regionalisation for Australia (IBRA), it was first defined by John Stanley Beard in 1980.

The Avon Wheatbelt is a bioregion in Western Australia. It has an area of 9,517,104 hectares. It is considered part of the larger Southwest Australia savanna ecoregion.