Sir Joseph Whitworth, Baronet (December 21, 1803 – January 22, 1887) was an English engineer and entrepreneur.

Early life and career
Whitworth popularized a method of producing accurate flat surfaces during the 1830s, using engineer's blue and scraping techniques on three trial surfaces. Up until his introduction of the scraping technique, the same three plate method was employed using polishing techniques, giving less accurate results. This led to an explosion of development of precision instruments using these flat surface generation techniques as a basis for further construction of precise shapes.
His next innovation, in 1840, was a measuring technique called "end measurements" that used a precision flat plane and measuring screw, both of his own invention. The system, with an accuracy of one millionth of an inch, was demonstrated at the Great Exhibition of 1851.
In 1841 Whitworth devised the first standardized system for screw threads. Its adoption by the railway companies, who until then had all used different screw threads, led to its widespread acceptance. It later became a British Standard, "British Standard Whitworth", abbreviated to BSW and governed by BS 84:1956.
Whitworth was commissioned by the War Department of the British government to design a replacement for the calibre .577-inch Pattern 1853 Enfield, whose shortcomings had been revealed during the recent Crimean War. The Whitworth rifle had a smaller bore of 0.45 inch (11 mm) which was hexagonal, a longer bullet and tighter rifling than the Enfield, and its performance during tests in 1859 was superior to the Enfield's in every way. The test was reported in The Times on April 23 as a great success. However, the new bore design was found to be prone to fouling, so it was rejected by the British government, only to be adopted by the French Army. Some of these rifles found their way to the Confederate states in the American Civil War, where they were called "Whitworth Sharpshooters".
The Enfield rifle was converted to Snider-Enfield Rifle by Jacob Snider, a Dutch-American wine merchant from Philadelphia. By converting existing Enfield rifles this way, the cost of a "new" breech-loading Snider-Enfield rifle was only 12 shillings.
Queen Victoria opened the first meeting of the British Rifle Association at Wimbledon, in 1860 by firing a Whitworth Sharpshooter from a mechanical rest. The rifle scored a bull's eye at a range of 400 yards (366 m).
Whitworth also designed a large Rifled Breech Loading gun with a 2.75 inch (70 mm) bore, a 12 pound 11 ounce (5.75 kg) projectile and a range of about six miles (10 km). The spirally-grooved projectile was patented in 1855. This was also rejected by the British army, who preferred the guns from Armstrong, but was also used in the American Civil War.
While trying to increase the bursting strength of his gun barrels, Whitworth patented a process called "fluid-compressed steel" for casting steel under pressure, and built a new steel works near Manchester. Some of his castings were shown at the Great Exhibition in Paris ca. 1883.
Whitworth received many awards for the excellence of his designs, and was financially very successful. In 1850, then a Fellow of the Royal Society and President of the Institution of Mechanical Engineers, he built a house called The Firs in Fallowfield, south of Manchester. In 1854 he bought Stancliffe Hall in Darley Dale, Derbyshire. In 1872 he moved there with his second wife.
A strong believer in the value of technical education, Whitworth backed the new Mechanics' Institute in Manchester, which was to become UMIST, and helped found the Manchester School of Design. In 1868, he founded a scholarship for the advancement of mechanical engineering. In recognition of his achievements and contributions to education in Manchester, the Whitworth Building of the University of Manchester's Main Campus is named in his honour, as well as the University Halls of residence "Whitworth Park" and one of the main streets in Manchester's city centre, "Whitworth Street".