The sonic screwdriver is a fictional tool in the British science fiction television series Doctor Who. Its most common function is to operate virtually any lock, mechanical or electronic, and thus open doors for escape or exploration. It has also been used for repairing equipment, as an offensive weapon, and occasionally even to drive screws. Like the TARDIS, it has become one of the icons of the programme, and is closely associated with the Doctor.

The sonic screwdriver made its first appearance in the serial Fury from the Deep, written by Victor Pemberton. It was then used by the Second Doctor as a multi-purpose tool from that point, with occasional variations in appearance over the course of the series. However, ownership of the concept was retained by the BBC, much to the chagrin of Pemberton, who later told an interviewer for Doctor Who Magazine, "I'm very cross that the sonic screwdriver — which I invented — has been marketed with no credit to myself. ... It's one thing not to receive any payment, but another not to receive any credit."[1] Its abilities varied somewhat from story to story and the way it worked was never explicitly explained. However, the name implies that it operates through the use of sound waves to remotely exert physical forces on objects, such as the mechanisms inside locks (The name also implies that it is used to drive screws, so that may be best taken with a grain of salt. However, it may be so it was originally made for that function, but was capable of doing much more). In The Three Doctors, it functions as a radiation detector. In The Sea Devils the Doctor used it to detonate land mines from a distance, which he did again later in Robot. This particular model had a movable section that bobbed up and down when in use. Also in Robot, the Doctor used the screwdriver as a "miniature sonic lance" to cut out a lock. The Doctor's Time Lady companion Romana constructed a sonic screwdriver of her own, first seen during the Fourth Doctor serial City of Death. It was smaller and sleeker than the Doctor's, and he was sufficiently impressed with her design that he attempted (unsuccessfully) to swap screwdrivers with her in Horns of Nimon. The sonic screwdriver was written out of the series in 1982 when it was destroyed by a Terileptil in the Fifth Doctor serial The Visitation in order to prevent the Doctor from escaping captivity. This was done by Eric Saward on the instructions of producer John Nathan-Turner, who felt that the device had become an easy way out for writers, since the Doctor could use it to get out of just about any situation. Saward had written out the sonic screwdriver believing that the Doctor would simply get a replacement from the TARDIS. However, Nathan-Turner did not want such a scene at the end of this story, or any others. The series remained sonic screwdriver-free until it ceased production in 1989 (although the Sixth Doctor was occasionally seen using a "sonic lance") and it was not until the 1996 Doctor Who telemovie that the Doctor was seen to have a sonic screwdriver again, with a design that could be telescoped out for use and collapsed again when finished.