William Edward Colby (May 28, 1875 – November 9, 1964) was an American lawyer, conservationist, and the first Secretary of the Sierra Club.

William Colby was born in Benicia, California and was brought up by his aunt after being orphaned at the age of six.

Colby joined the Sierra Club in 1898, the year of his graduation from law school.

[1] In 1905, when the city of San Francisco lobbied Congress to allow it to dam the Hetch Hetchy Valley to provide the growing city with water, Muir and Colby were leaders of the campaign to prevent the damming of the Tuolumne River and the flooding of the valley.

[3] Other members of the State Park Commission included:[4] Major Frederick R. Burnham, W. F. Chandler, Henry W. O'Melveny, and Dr. Ray Lyman Wilbur.