A letter patent (pl. letters patent) is a type of legal instrument in the form of a published written order issued by a monarch or president, generally granting an office, right, monopoly, title, or status to a person or corporation. They are so named from the Latin verb pateo, to lie open, exposed, accessible, being called in full litterae patentes.

Letters patent can be used for the creation of corporations or government offices, or for the granting of city status or a coats of arms. A particular form of letters patent has evolved into the modern design patent granting exclusive rights in an invention. Clearly in this case it is essential that the written grant should be in the form of a public document so other inventors can consult it to avoid infringement.

The opposite of letters patent are letters close (Latin: litterae clausae), which are personal in nature and sealed so that only the recipient can read their contents.

Letters patent are a form of open or public proclamation and a vestigial exercise of extra-parliamentary power by a monarch or president. Prior to the establishment of parliament, the monarch ruled absolutely by the issuing of his personal written orders, open or closed.

Nikola Tesla (Serbian Cyrillic: Никола Тесла; 10 July 1856 – 7 January 1943) was a Serbian-American inventor, physicist, mechanical engineer, electrical engineer, and futurist. He was an important contributor to the use of commercial electricity, and is best known for developing the modern alternating current (AC) electrical supply system. His many revolutionary developments in the field of electromagnetism in the late 19th and early 20th centuries were based on the theories of electromagnetic technology discovered by Michael Faraday. Tesla's patents and theoretical work also formed the basis of wireless communication and the radio.

Born in the village of Smiljan (now part of Gospić, present day Croatia), Tesla was a subject of the Austrian Empire by birth and later became an American citizen. Because of his 1894 demonstration of short range wireless communication through radio and as the eventual victor in the "War of Currents", he was widely respected as one of the greatest electrical engineers who worked in America. He pioneered modern electrical engineering and many of his discoveries were of groundbreaking importance. In the United States during this time, Tesla's fame rivaled that of any other inventor or scientist in history or popular culture. Tesla demonstrated wireless energy transfer to power electronic devices in 1891, and aspired to intercontinental wireless transmission of industrial power in his unfinished Wardenclyffe Tower project.