Linus Yale Jr. (April 4, 1821 – December 25, 1868) was an American businessman, inventor, mechanical engineer, and metalsmith. He was a co-founder with millionaire Henry R. Towne of the Yale Lock Company, which became the premier manufacturer of locks in the United States. He was the country's leading expert on bank locks and its most important maker. By the early 20th century, about three-quarters of all banks in America used his bank locks. He is best remembered for his inventions of locks, especially the cylinder lock, and his basic lock design is still widely distributed today, and constitutes a majority of personal locks and safes.

Linus Yale Jr. was born in Salisbury, New York. His ancestors were of the same family as Elihu Yale, the benefactor to and namesake of the well known Yale University. The Yale family of America were all descended from the same ancestor, Thomas Yale, Elihu's only uncle with the Yale name. Thomas Yale was the stepson of Governor Theophilus Eaton.

Yale's father, Linus Yale Sr., opened a lock shop in the 1840s in Newport, New York, specializing in bank locks; he was a successful inventor who specialized in expensive, handmade bank locks and mechanical engineering, and who held eight patents for locks and another half dozen for threshing machines, sawmill head blocks, and millstone dressers.

After some regular education, Yale Jr. joined his father's business and introduced some revolutionary locks that utilized permutations and cylinders. In 1857, he established the Yale & Greenleaf Lock Co. with his future brother-in-law, Congressman Halbert S. Greenleaf, who also financed the venture. In 1858, Yale's father died, and Linus Yale Jr. became more involved with his father's lock company. Yale Jr. was joined in the family business by his cousin, Charles Oscar Yale, who was also a prolific lock inventor with several patents.

Yale opened his own shop about 1860 in Shelburne Falls, Massachusetts, specializing in bank locks. He later founded a company with millionaire Henry Robinson Towne in the South End section of Stamford, Connecticut, called the Yale Lock Manufacturing Company. Throughout his career in lock manufacturing, Yale acquired numerous patents for his inventions and received widespread acclaim from clients regarding his products.

Linus was personal friends and frequent correspondent with the abolitionist Congressman William Morris Davis.

Young Yale developed an early affinity for portrait painting, but about 1850 switched interests to assist his father with improving bank locks and studying mechanical problems. However, his artistic expertise later proved useful, sketching clear and accurate diagrams for his later lock designs.

In the 1860s, around the time he had opened his own shop in Shelburne Falls, Massachusetts, Yale specialized in bank locks. He introduced some combination safe locks and key-operated cylinder locks that were improvements on previously used locks. Possessing admirable skills in mechanics and lock making, Yale created one of the first modern locks that used a pin-tumbler design.