Eucalyptus foecunda, commonly known as narrow-leaved red mallee, is a species of plant that is endemic to Western Australia. It has rough bark on the trunk, smooth bark above, narrow lance-shaped adult leaves, flower buds in groups of nine or eleven, creamy white flowers and cup-shaped fruit.

Eucalyptus foecunda is a mallee that typically grows to a height of 3 m to 5 m and forms a lignotuber. The bark is flaky at the base, otherwise smooth, grey and reddish-brown in colour. Young plants and coppice regrowth have dull green, elliptic to lance-shaped leaves that are 40–80 mm and 2–20 mm wide. Adult leaves are narrow lance-shaped to narrow oblong, the same glossy green on both sides, 50–95 mm and 5–13 mm wide on a petiole 5–17 mm long.

The flower buds are arranged in leaf axils in groups of nine or eleven on an unbranched peduncle 5–13 mm long, the individual buds on pedicels 2–5 mm long. Mature buds are oval to spindle-shaped, 6–10 mm and 3–4 mm wide with a conical or beaked operculum 2.5–6 mm long. Flowering occurs in August or from January to February and the flowers are creamy white. The fruit is a woody, cup-shaped capsule 4–6 mm long and wide.

This mallee has a similar appearance to Eucalyptus petrensis but E. petrensis has a more persistent style on the fruit.

Narrow-leaved red mallee grows on limy sands near the coast of Western Australia between Lancelin and Mandurah.