R-18

R18, or R-18, may refer to:

* R18 certificate, a film or video classification given by a number of agencies:
** the British Board of Film Classification
** the Office of Film and Literature Classification (Australia)
** the Office of Film and Literature Classification (New Zealand)
* R-18, a motion picture rating in Japan and the Philippines
* , a risk phrase in chemistry
* USS R-18 (SS-95), an R-class coastal and harbor defense submarine of the United States Navy
* Renault 18, a French automobile