Chaetomorpha linum is a species of green algae in the family Cladophoraceae.

[2] Chaetomorpha linum is a species composed of fine hair-like, uniseriate, unbranched filaments.

Cells 1 - 2 times as long as broad, maximum width 585μm.

[3] Both unattached (C. linum) and attached (C. aerea) forms exist.

[1] Both C. linum and C. aerea are found around the British Isles and around Europe into the Mediterranean and Mar Menor.