Two Sphagnum species are reported for Hawaii: S. palustre L. (section Sphagnum) and S. wheeleri C. Müll. (section Rigida). Sphagnum henryense Warnst. (section Sphagnum) is excluded. Additional evidence supporting the exclusion of Sphagnum vitjianum Schimper and S. perichaetiale Hampe (both in section Sphagnum) is also presented. The type of S. lonchocladum C. Müll. is shown to be a Hillebrand collection (in section Sphagnum) from Hawaii and not a Kirk collection (in section Rigida) from New Zealand. The description of S. palustre is revised, in large part to reflect the incorporation of S. japonicum Warnst., S. pseudocymbifolium C. Müll, and S. sulphureum Warnst.