Eucalyptus sinuosa, commonly known as Octopus Mallee, is a species of mallee that is endemic to Western Australia. It has smooth bark, linear leaves, flower buds fused together in clusters of between eleven and twenty-five, greenish yellow flowers and fruit that are fused into a woody mass. Eucalyptus sinuosa is a mallee that typically grows to a height of 4 m and forms a lignotuber. The bark is smooth, cream-coloured, grey to grey-brown and orange-brown and is shed in strips and short ribbons. Flowering occurs between December and April and the flowers are yellow green. The fruits are fused into a woody mass 25–75 mm in diameter, including the strongly protruding valves.