Sigríður Tómasdóttir (1871–1957) was an Icelandic environmentalist whose activism helped preserve Gullfoss waterfalls, protecting it from industrialization.

[2] In 1907, landowners including Sigríður's father, Tómas Tómasson, signed a deal to allow the construction of a hydroelectric dam across the Hvítá River that would result in the submergence of Gulfoss.

[3] She made numerous treks of 120 kilometers to Reykjavík, by some accounts on foot, to meet with government officials and later threatened to throw herself in the waterfalls.

Tómasdóttir's efforts ultimately failed with the legal system but gained positive public attention.

[1][3] Gullfoss and the surrounding area was eventually sold to the Icelandic government and was made a permanent conservation site in 1979.