An open secret is a concept or idea that is "officially" secret or restricted in knowledge, but is actually widely known; or refers to something which is widely known to be true, but which none of the people most intimately concerned are willing to categorically acknowledge in public.

Examples of military open secrets:

Completed in 1964, the BT Tower, despite being a 177-metre (581 ft) tall structure in the middle of central London, was an official secret and did not appear on Ordnance Survey maps until it was officially revealed by Kate Hoey under parliamentary privilege in 1993.

Kayfabe, or the presentation of professional wrestling as "real" or unscripted, is an open secret, kept displayed as legitimate within the confines of wrestling programs but openly acknowledged as predetermined by wrestlers and promoters in the context of interviews for decades.

An example of an open secret in politics is that it may be widely known that an individual government minister holds a particular opinion, but is at present unable to express that opinion publicly because it is contrary to the formally expressed view of the government of which he or she is a member.

Stephen Arthur Stills (born January 3, 1945) is an American guitarist and singer/songwriter best known for his work with Buffalo Springfield and Crosby, Stills & Nash (and Young). He has performed on a professional level in several other bands as well as maintaining a solo career at the same time. Stills was ranked #28 in Rolling Stone Magazine's 2003 list of "The 100 Greatest Guitarists of All Time". Stills became the first person to be inducted twice on the same night into the Rock and Roll Hall of Fame for his work with CSN and the Buffalo Springfield.

Stills was raised in a military family. Moving around as a child, he developed an interest in blues and folk music. He was also influenced by Latin music after spending his youth in Gainesville and Tampa, Florida, Louisiana, Costa Rica, Panama Canal Zone and El Salvador, where he graduated from high school, and was an avid sailor. He also attended Admiral Farragut Academy in St. Petersburg, Florida and Saint Leo College Preparatory School in Saint Leo, Florida.

Jon Hassell (born March 22, 1937) is an American trumpet player and composer. He is known for his influence in the world music scene and his unusual electronic manipulation of the trumpet sound.

Born in Memphis, Tennessee, Hassell received his Master's degree from the Eastman School of Music in Rochester, New York. During this time he became involved in European serial music, especially the work of Karlheinz Stockhausen, and so after finishing his studies at Eastman, he enrolled in the Cologne Course for New Music for two years (founded and directed by Stockhausen). Hassell returned to the U.S. in 1967, where he met Terry Riley in Buffalo, New York and performed on the first recording of Riley's seminal work In C in 1968. He pursued his PhD in musicology in Buffalo and performed in La Monte Young's "Dream House" (aka Theatre of Eternal Music) in New York City.

On his return to Buffalo in the early 1970s, Hassell was introduced to the music of Indian Pandit Pran Nath, a specialist in the Kiranic style of singing. Hassell, Young, Marian Zazeela (Young's wife) and Riley went together to India to study with Nath. His work with Nath awoke his appetite for world music, and on the album Vernal Equinox, he used his trumpet to imitate the vocal techniques of Nath (treated with various electronic effects) where he stated: