Nyaania Creek (31°55′S 116°03′E / 31.91°S 116.05°E) is a creek in Western Australia. It is a seasonal tributary that flows into the Helena River with a catchment that moves through a number of hills suburbs just east of the Darling Scarp. Its source is in Mahogany Creek, and it flows through Glen Forrest, Darlington, and Boya before meeting the Helena River at Helena Valley.
It was originally known as the Smiths Mill Brook on maps between 1902 and 1920. In the 1920s it became known as Nyaania Brook, and in 1945 it officially took the current name.
Its importance stems from the fact that it flows through private land for most of its length, linked to issues that affect watercourses in the Darling Scarp region:
It has significant areas of reserves either adjacent, or within 100 metres (330 ft) either side of its main creek bed. It runs in a number of places along what was rail reserve of the Eastern Railway – which is now the southern part of the Railway Reserve Heritage Trail.