William Johnson (December 8, 1821 – October 10, 1875) was a New York State businessman and politician.

The Johnson residence still stands on Cayuga Street in Seneca Falls, and is being developed into condominiums after years as a home for women.

He resigned his commission and returned to New York in late 1863, citing ill health, but continued to support the Union cause at home.

He was elected to the New York State Senate in the fall of 1871, as a Democrat representing the 26th District, then comprising Ontario, Seneca, and Yates counties.

Being charged with only 30 days in which to act on the matter, Johnson used what he viewed as Republican attempts at interference as leverage to aid in the passage of his bill for the creation of an investigatory panel.

During his second term as a State Senator, he was a member of the committees on Canals, Manufactures, and Militia.