William Healey Dall (August 21, 1845 – March 27, 1927) was an American naturalist, a prominent malacologist, and one of the earliest scientific explorers of interior Alaska.

Dall also made substantial contributions to ornithology, zoology, physical and cultural anthropology, oceanography, and paleontology.

His father Charles Henry Appleton Dall, (1816–86), a Unitarian minister, moved in 1855 to India as a missionary.

His family however stayed in Massachusetts, where Dall's mother Caroline Wells Healey was a teacher, transcendentalist, reformer, and pioneer feminist.

Kennicott was selected as the scientist for this expedition, and with the influence of Spencer Fullerton Baird of the Smithsonian Institution, he took Dall as his assistant, because of his expertise in invertebrates and fish.

Aboard the clipper Nightingale, under the command of the naturalist Charles Melville Scammon, Dall explored the coast of Siberia, with first several stops in Alaska (still Russian territory at that time).

On a stop at St. Michael, Alaska, he was informed that Kennicott had died of a heart attack on May 13, 1866, while prospecting a possible telegraph route along the Yukon River.

This was uncharted country, with a fauna and flora still waiting to be explored and described, a task Dall took upon himself as a surveyor-scientist.

His official mission was to survey the Alaska coast, but he took the opportunity to acquire specimens, which he collected in great numbers.

In 1874 aboard the United States Coast Survey schooner Yukon, he anchored in Lituya Bay, which he compared to Yosemite Valley in California, had it retained its glaciers.

He was assigned to the U.S. National Museum as honorary curator of invertebrate paleontology, studying recent and fossil mollusks.

Dall was the undisputed expert on Alaska, and the scientists aboard were often surprised by his erudition, both in biology and in respect to the cultures of the native Alaskan peoples.