Juncus ingens, common name giant rush, is a dioecious perennial with horizontal or ascending rhizomes.

The stems are erect, dull green, (1.5–2–5 m tall and 4–10 mm in diameter, cataphylls are to 40 cm or more long.

[4] Juncus ingens is native to the floodplains of southeastern Australia, occurring mainly in Victoria,[5] forming dense stands on the margins of seasonal wetlands.

[2] Although native to Australia, Juncus ingens is considered an invasive species in some areas such as Barmah National Park.

[7][8] The spread of J. ingens into areas where it historically did not occur is a result of changes to flooding regimes in the now highly regulated Murray-Darling Basin.