Eucalyptus macarthurii, commonly known as the Camden woollybutt or Paddy's river box,[2] is a species of medium-sized tree that is endemic to a small area of New South Wales.

It has rough, fibrous bark on the trunk and larger branches, smooth above, narrow lance-shaped to curved adult leaves, flower buds in groups of seven, white flowers and small conical to bell-shaped fruit.Eucalyptus macarthurii is a tree that typically grows to a height of 40 m (130 ft) and forms a lignotuber.

[2][3][4][5] Eucalyptus macarthurii was first formally described in 1899 by Henry Deane and Joseph Maiden in Proceedings of the Linnean Society of New South Wales.

[6] The specific epithet (macarthurii) honours "Sir William Macarthur, who appears to have been the first to recognise this particular Woolly-butt as a distinct tree".

[7] Camden woollybutt grows in open forest on flats and near watercourses on the Central and Southern Tablelands between the Blue Mountains and Goulburn.