Warren Olney, Sr. (March 11, 1841 – June 2, 1921) was an American lawyer, conservationist, and politician, in California.

He was a founding member, alongside John Muir and the young botany professor, Willis Linn Jepson of the University of California at Berkeley, of the Sierra Club.

During that time, one of the students in his school was to become a famous (or infamous as may be) future western hero, Wyatt Earp.

His unit held and fought well before breaking and running in the general rout ending the first day's battle.

Though too spent to penetrate, the bullet that struck Olney left him too stiff and sore to take any part in the second day's actions.

However, he seems not to have received word of his release from service and returned to his unit remaining with it until his final discharge in August 1865.

[7][8] Done with military service, he returned to Iowa to marry his college sweetheart and attended the University of Michigan, there earning a degree in law.

Loving the high places and magnificent countryside in California he made acquaintance with John Muir, Willis Linn Jepson, and other like minded people.

He held strong views that California cities and communities needed a secure water supply system separate from private independent suppliers.

Olney supported this project, resulting in a bitter separation from John Muir, his other conservationist friends, and with the Sierra Club, who staunchly opposed the environmental destruction.

His grandson, Warren Olney III was appointed by President Dwight D. Eisenhower as an Assistant Attorney General to oversee the Criminal Division of the United States Department of Justice.