Phaeosaccion is a genus of algae with monostromatic tubular to saccate thalli, up to 20 centimetres (7.9 in) long and to 2 centimetres (0.79 in) wide.

[1] It is olive brown and resembles young plants of Scytosiphon.

Farlow in the article Notes on New England algae published in Bulletin of the Torrey Botanical Club in 1882.

[2] It was named in honor of Frank Shipley Collins.

[3]: 56  Phaeosacchion collinsii is red listed in Iceland as a vulnerable species (VU).