Fimbristylis macassarensis is a sedge of the family Cyperaceae that is native to Australia.

The annual grass-like or herb sedge typically grows to a height of 0.06 to 0.4 metres (0.20 to 1.31 ft) and has a tufted habit. It blooms between February and June and produces green-brown flowers.

In Western Australia it is found on along creeks and rivers and other damp places in the Kimberley region where it grows in red sandy-clay soils often over basalt.

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