The locking pin assembly includes an elongate pin housing and a pin mechanism insertably mounted into a bore in the pin housing. The pin mechanism includes at least one rotator section integral with a pin shaft. A rotation-locking member is integrally attached to the bottom of the pin shaft, the locking member having a non-circular shape. An elongate post having a rotation-locking collar attached to one end of the post is slidable in a keyhole extending through the pin. A non-circular recess is formed in the rotation-locking collar, which selectively receives the locking member therein. A spring is disposed behind the rotation-locking collar. The spring normally biases the locking collar into engagement with the locking member. A key is provided to axially push the post to selectively disengage the locking member for selective rotation of the rotator section between locked and unlocked positions.