A sex doll is a type of sex toy, imitating a human body for simulated sexual acts. The sex doll may consist of an entire body with face, or just a pelvic part, with the openings (vagina, anus, mouth) for copulation. The openings are sometimes vibrating and may be removable or interchangeable.

There has long been a sailor's term, the "dame de voyage", or "dama de viaje" in French and Spanish respectively, indicating a female doll made of sewn cloth and used by sailors aboard ship. They were first developed in their modern form by Japan and Germany during the late 1930s and early 1940s - in Germany as part of the military 'Model Borghild' project, and in Japan for use on naval submarines. In both instances, the aim was to give sexual relief to men confined in an all-male environment. 'Bild Lilli doll' was a mid 1950s German doll marketed as a sex toy for men, and whose design is reputed to have inspired Ruth Handler to make the first Barbie doll for girls.

A 1982 attempt to import a consignment of sex dolls into Britain had the unintended consequence of lifting all import prohibitions on "obscene or indecent" items arriving from Europe. Having had the dolls seized by Her Majesty's Customs and Excise officers, Conegate Ltd. took the case all the way to the European Court of Justice, and won in 1987 (1). Britain was forced to lift its stringent import prohibitions dating from 1876, because to do otherwise would have constituted an arbitrary barrier to free trade under the terms of the Treaty of Rome.

Cheaper sex dolls are inflatable, using air. These lower price-range (less than $50) dolls are usually rather ugly, made of welded vinyl, and bear only a passing resemblance to women or men, but they have an (artificial) vagina or penis and their users are willing to overlook their shortcomings. They often burst at the seams after a few uses. Cheap vinyl dolls may be a health risk, if they contain large amounts of dangerous vinyl chloride or phthalates.

At the middle market price-range ($100 to $200), dolls are made of heavy latex without welded seams, have plastic mannequin-style heads and styled wigs, plastic or glass eyes, and properly moulded hands and feet. Some contain water-filled body areas. The manufacturing process causes most latex dolls to be delivered with a fine coating of zinc oxide covering the skin, and this should be removed by showering. Otherwise, latex is an inert and non-toxic natural material; although a tiny percentage of users may discover a latex allergy. All latex dolls of any quality currently on the market are manufactured in either France or Hungary.

More expensive sex dolls ($600 to $5,000 or more) are made from silicone. They can be very lifelike, with face and body modelled on real women or men, with realistic skin material (similar to that used for movie special effects), with realistic (or real) hair. These dolls usually have an articulate PVC or metal skeleton with flexible joints that allows them to be positioned in a variety of positions for display and for sexual acts. Silicone sex dolls are obviously heavier than inflatable ones (which consist of mostly air), but are about half the weight of a real human of comparable size. They are made in the USA by Abyss Creations (the Realdoll), 1st-PC, Mimicon and others; and in Japan by Paper Moon, 4Woods, Orient Industries and others.

Silicone dolls are quite popular in Japan, where they are known as "Dutch Wives" ('datch waifu'). Their name originates from the term, possibly English, for the thick rattan or bamboo bolster, used to aid sleep in humid countries by keeping one's limbs lifted above sweaty sheets. There is even a rental service for 'datch waifu' in Tokyo, Doru no Mori, that specialises in sex dolls.

The middle market and high-end market emerged in the USA around 1995. The market has grown for two main reasons. Firstly, the last twenty years have seen huge improvements over earlier types of sex doll, and customers come to realize this through using the web. Secondly, the method of retail purchase has also improved - customers now select online instead of having to take "pot luck" in a sex shop, and a possible purchase can be discussed first in online forums with existing owners. Extras to customise a doll to one's personal taste (wigs, clothes, perfumes, etc) can also be purchased discreetly online.

The Realdoll has evolved since 1995, and the latest models are significant improvements over those of just a few years ago. The success of the Realdoll has led others to enter the market for high-end dolls, often using new proprietary materials.

A company called CybOrgasMatrix uses a new material - a very elastic gel with a strong shape memory, which, they claim, is superior to silicone in quality and also cheaper. Their sex doll product includes additional features, such as pelvic thruster motor and audio capability (using wireless headphones).

The ongoing advances in robotics suggest that sex robots may be eventually manufactured and sold. A stepping stone to the implementation of full robotics would be to embed some of the rapidly developing cybersex technologies in dolls, to enable telepresence sexual activity. Spin offs from new technologies will undoubtedly be introduced into sex dolls - such as minaturization, voice response, 'smart materials' and 'intelligent textiles'. Science-fiction and post-feminist theorists have already imagined a variety of artificial women, or gynoids.

In June 2006, Henrik Christensen of the European Robotics Research Network (Euron) told the UK's Sunday Times that: "People are going to be having sex with robots within five years".

In Japan inflatable love pillows ('dakimakura') with a life-size picture of a porn star or anime character and optionally a hole for lovemaking are also popular.

Some inflatable sex dolls are made in the form of animals, most notably sheep. These dolls are more of a joke gift or party novelty.

Sex dolls appear occasionally in comedy shows and movies. Notably, the Ally McBeal series integrated one into the plot, regularly showing Ally dancing and sleeping with an inflatable male sex doll.

Sex dolls have been the subject of numerous punk and rock songs, most notably by Roxy Music, Frank Zappa, Saul Zonana and The Police.

The Swedish webcomic Little Gamers features Marcus, a character who has never had sex with a real girl, only with inflatable dolls. These inflatable dolls are a running joke in the comic.

Novels centering on sex dolls include Richard Calder's Dead Girls. Cinema-release movies include Monique (France, Valerie Guignabodet, 2002), Love Object (US, Robert Parigi, 2003),Life Size (Tamaño Natural, 1973), and Ghost in the Shell 2: Innocence (Japan, 2004).

Sex dolls and sexualized mannikins have appeared in art photography, notably that of Elena Dorfman and Anoush Abrar. Two feature-length documentaries about sex dolls and their owners are set to premiere at U.S. film festivals in 2006.