Rich black is a term used in printing to refer to a mixture containing all four of the cyan, magenta, yellow and black (CMYK) colors. Less frequently it could be mixture of black and some other ink.

Rich black is a color that is "blacker than black". While this is nonsense from the point of view of color theory, the difference can often be seen in the printed piece.

The use of rich black has to be based on a full understanding of the printing conditions, including the inks, printing press and especially the paper. If too much ink is used on poor quality paper such as newsprint it may simply fall apart. In addition, excessive amounts of ink may not have a chance to dry before the printed result comes into contact with other pages. Finally, rich black, because it uses more ink, will have higher costs.

Another reason to use rich black for small areas of black is to avoid trapping issues. Rich black is often used for text printed over a picture or colored background, because otherwise any slight mis-registration between printing plates would produce a white or colored halo around the text. Making it much harder to read.

In some cases the process of preparing a work to print may include conversions to CMYK from RGB or other color spaces. The amount of black mixed with C,M,Y inks can be expressed as a process of under color removal or under color addition, though increasingly the entire conversion process is done using an ICC profile which expresses both the conversion and the under color handling.