John Lenthall (1807–1882) was an important American shipbuilder and naval architect in the mid-19th century. He was responsible for the construction and repair of United States Navy ships during the American Civil War (1861–1865), as well as in the years immediately before and after it. His career spanned the U.S. Navy‍ '​s transition from sail to steam propulsion and from wooden ships to ironclads, and in retirement he participated in early planning for an eventual steel navy.