Stanley Kubrick made Anthony Burgess' controversial sci-fi novel "A Clockwork Orange" into film - and created a movie that is nowadays critically acclaimed and said to be the "Movie of the 20th century".
Unfortunately, when the movie was released in 1971, the masterpiece was only seen as a nightmare full of sex, violence and Beethoven. In many countries, the movie was forbidden; in the United States, the movie got an "X"-Rating - usually, only porno movies receive an X-Rating.

In many countries, even the film poster was censored. The following report will go into this a little more detailed:

Here you can see the uncensored film poster:
The reason why the film poster was censored is the fact, that underneath Alex you can see a naked woman (the statue from the Korova Milk Bar). This was too much to show for many moralizers in the USA - you could see naked breasts and the female genitalia was only covered by the tip of the triangle. Therefore, the decision was made to censor the film poster.

Here you can see the censored film poster:
It shows that film posters are no exception of the prudish attitude, that a naked body is not okay to show in the USA - obviously not even if its a matter of art.
Out of moral considerations, the woman was dressed with a bra and a pair of panties.

Here you can see the current film poster which is also censored.
For the reissue of the movie the woman was completely removed from the picture. Now it only shows Alex' face.
Unfortunately, this version of the film poster was used everywhere - the original uncensored version seems to be forgotten!