Onslow Stearns (August 30, 1810 – December 29, 1878) was an American businessman and politician who served as the 32nd governor of New Hampshire.

He attended the local schools of his hometown, and moved to Boston, where he clerked in several stores in preparation for a business career.

In 1857 Stearns received the honorary degree of Master of Arts from Dartmouth College.

He served as the Senate's President pro tempore in 1863, and was a Delegate to the 1864 Republican National Convention.

During his time in office the state created a board of agriculture, taxes and deficits necessitated by New Hampshire's participation in the American Civil War were lowered, and the state government continued to promote the development of railroads and manufacturing business.