Aloe marlothii (also known as the mountain aloe or the flat-flowered aloe) is a large, single-stemmed Southern African aloe of rocky places and open flat country, occasionally growing up to 6m tall.
Named after Rudolf Marloth, a South African botanist, this species of aloe has an especially large robust head of stiff, grey-green leaves. These leaves can be up to 1.5m in length and usually densely covered in short spines on the convex lower surfaces and less so on the concave upper surfaces. Like many other arborescent aloe species, this Aloe is more spiny when it is small and as it becomes taller and less vulnerable to grazing, it loses many of the spines from its leaf surfaces. It normally has a trunk densely covered by the withered old leaves.