Apium prostratum, commonly known as sea celery, is a variable herb native to coastal Australia and New Zealand. The leaves are variable, with toothed leaflets, and a celery like aroma. The tiny white flowers occur in clusters.

There are two varieties:

• Apium prostratum var. filiforme – headland sea celery, squat with broad leaves (2-3 times longer than wide)and grows on coastal dunes and headlands.
• Apium prostratum var. prostratum – mangrove sea celery, upright with fine leaves (6-15 times longer than wide) and grows in swamps.

The subspecies Apium prostratum subsp. howense is endemic to Lord Howe Island.

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