The first Space Shuttle orbiter, a real NASA test vehicle named Enterprise after a letter-writing campaign by Star Trek fans, and later woven into the franchise's own lineage of ships bearing the name.
Enterprise, designated OV-101, was the prototype orbiter of NASA's Space Shuttle programme. It was originally to be called Constitution, but a write-in campaign by Star Trek viewers persuaded the White House to rename it, and members of the original cast attended its roll-out in California in 1976. It flew approach and landing tests in 1977 but never travelled to space.
Within the fiction the shuttle is treated as an ancestor of the starships. Its picture hangs on the recreation deck in Star Trek: The Motion Picture among earlier vessels named Enterprise, it is seen in the opening titles of Star Trek: Enterprise, and a model of it sits in Admiral Marcus's office in Star Trek Into Darkness.