Mullum Mullum Creek, Natural brook in City of Whitehorse, Australia.

Mullum Mullum Creek runs 22 km from Croydon through Ringwood, Mitcham, Donvale, East Doncaster and Warrandyte to the Yarra River. Its bed of silt gives the water a green-brown colour, light brown after heavy rain. The creek is divided into four sections: the High Plateau Tract, the Mullum Mullum Gorge with its rocky cascades and tree ferns, the Valley Tract and the Plains Tract.

The Wurundjeri people of the Kulin nation used the creek for tens of thousands of years as a sustainable source of food and tools. In the 1990s, the Mullum Mullum Valley became a focus of Melbourne's eastern suburbs for housing estates and native vegetation regeneration. The Eastlink Tollway, opened in 2008, passes through 1.5 km of tunnels under the gorge to avoid disturbing the remnant ecosystem, but crosses the creek above ground in Ringwood, where the creek was relocated.

Mullum Mullum is adapted from Woiwurrung and is thought to mean "place of many big birds", which led some historians to read it as "Place of Eagles". Others propose "place of many big swifts" or "place of many big owls", possibly referring to the powerful owls of the valley. Some suspect it mistranslates Ballum Ballum, "place of many butterflies", as grassy woodlands here breed many undocumented butterfly and moth species.

A trail follows the creek and connects multiple parks and recreational areas where visitors can walk, cycle, and observe wildlife throughout the year. Most access points are easy to reach and well marked.

The Eastlink Tollway crosses the valley through 1.5 km of tunnels bored to avoid cutting through the remnant ecosystem of the Mullum Mullum Gorge. At Ringwood, however, the road crosses the creek above ground, and the creek itself was relocated to make room for it.