Grevillea spinosissima is an shrub of the genus Grevillea native to an area in the Wheatbelt region of Western Australia. The spiny irregularly branched shrub typically grows to a height of 1 to 1.5 metres (3.3 to 4.9 ft) and has non-glaucous branchlets. It has simple, dissected, tripartite leaves with a blade that is 7 to 20 millimetres (0.28 to 0.79 in). It blooms from June to September and produces an axillary or terminal raceme regular inflorescence with white or cream flowers and white styles. Later it forms rugose oblong to ellipsoidal glabrous fruit that are 7 to 8 mm (0.3 to 0.3 in) long.