William Henry (December 12, 1775—September 2, 1836) was an English chemist.

William Henry, the son of Thomas Henry (1734-1816), an apothecary and writer on chemistry, was born in Manchester. He began to study medicine at Edinburgh in 1795, taking his doctor's degree in 1807, but ill-health interrupted his practice as a physician, and he devoted his time mainly to chemical research, especially with regard to gases. One of his best-known papers (Phil. Trans., 1803) describes experiments on the quantity of gases absorbed by water at different temperatures and under different pressures. His results are known today as Henry's law. His other papers deal with gas-analysis, fire-damp, illuminating gas, the composition of hydrochloric acid and of ammonia, urinary and other morbid concretions, and the disinfecting powers of heat.

His Elements of Experimental Chemistry (1799) enjoyed considerable vogue in its day, going through eleven editions in 30 years. This book was also translated into Japanese in 1840, as part of the Western studies "Rangaku" movement, by Utagawa Yoan under the name "Science of Chemistry" (舎密開宗, Seimikaisō).

He was one of the founders of the Mechanics Institute that was to become the University of Manchester Institute of Science and Technology.

He died at Pendlebury, near Manchester.

William Henry (May 19, 1729 – December 15, 1786) was an American gunsmith from Lancaster, Pennsylvania, and a delegate for Pennsylvania to the Continental Congress in 1784, 1785, and 1786.

Prior to his service in the Continental Congress, Henry was a gunsmith and provided rifles to the British during the French and Indian War and later the Continental Army during the American Revolution. Over a thirty-year period, Henry's gun factory in Lancaster not only supplied arms to Pennsylvanian and, later, Revolutionary troops (during the Revolution, his workmen were exempted from military service to ensure the continued production of necessary arms): Henry himself, serving as armorer, accompanied troops on Edward Braddock's disastrous expedition in the summer of 1755 to retake Fort Duquesne and again on John Forbes's successful mission in 1758.

Henry later served in many positions of public responsibility, including Assistant Commissary General to the Continental Army for the district of Lancaster and, in 1779, Commissary of Hides for Pennsylvania, Delaware, and Maryland. In these positions, Henry managed vast sums of money and acquired and transferred enormous amounts of material. In 1780 Henry informed Joseph Reed that he had "laid out…between Sixty & Seventy Thousand Pound" just to "purchase Leather and Paying Workmens Wages at the Shoe-Factory[s]" he had established "at Philadelphia, Allentown and Lancaster." His correspondence is filled with letters from Army leaders, including George Washington, begging for arms and other materials. Henry was also the Treasurer of Lancaster Country for many years, a position filled by his wife, Ann Wood Henry, from Henry's death in 1786 until her own in 1799.

Henry was also an intellectual. He helped found Lancaster’s Juliana Library-Company in 1759, which during the Revolution and after was housed in his residence, and he held membership in the American Philosophical Society in Philadelphia, whose first Transactions (1771) printed Henry's account of his invention of a "Description of a Self-Moving or Sentinel Register" to regulate the flue of a furnace. Henry also invented a screw auger, manufactured and sold exclusively at his Lancaster store, and some credit him with inventing the steamboat: the twelve-year-old Robert Fulton, a Lancaster neighbor, visited Henry in 1777, who had been experimenting since 1763 on boats with steam engines on the Conestoga River (Fulton's own experiments began only in 1786 in England). Henry was also the earliest patron of Benjamin West, who lodged in Henry's home in Lancaster in 1756 and painted portraits of William and Ann Henry, probably shortly after their marriage. More significantly, Henry encouraged West to paint "The Death of Socrates" (1756), perhaps the first history painting produced in the colonies ; West always credited Henry with having initiated the painter's interest in history painting, the genre for which the painter became so famous.

Henry's sons carried on his gun business, in Lancaster, in Philadelphia, in Nazareth, Pennsylvania, and then in Boulton, PA. One of his sons, John Joseph Henry, served as a sixteen year old rifleman on Benedict Arnold's march on Quebec in the fall and winter of 1775 (he was captured and imprisoned for much of 1776), and later served as president judge of the second District in Pennsylvania from 1795-1811.

William Henry (June 28, 1859 - March 20, 1928) was a British freestyle swimmer and lifesaver.

Henry was of Polish ancestry, and was born Joseph Nawrocki. He was a co-founder of the Royal Life Saving Society. As a swimmer he won a number of national and European championships. In 1906, at 47, he became the oldest ever Olympic medal winner in swimming as a member of the British 4x250 meter relay team which won the Bronze medal.

William Henry is an International Swimming Hall of Fame inductee.

William (Albert) Henry (November 10, 1914, Los Angeles, California - August 10, 1982, Los Angeles, California) was an American actor working in Hollywood movies. He started as a child actor, then was a hero in B-movies (mainly westerns), and ended his career as a character actor. He also appeared in various roles on episodes of many TV series. He was a member of the John Ford Stock Company and appeared twelve times for Ford. His older brother was the character actor Thomas Browne Henry.

William Henry, informally known as Willie Henry, is a Galway based author and historian. His topics usually concern natives of Galway or a Galway-related topic.

Debuted in films at the age of 8, and would then enjoy a well-rounded career first as juvenile actor, then B-movie hero and ultimately character player in his later years.