Negative selection (immunology) T-cells that recognize self MHC molecules (and peptides) with high affinity are deleted from the repertoire of cells. Tolerance is produced. Avoids auto-immunity. Occurs after positive selection.

Negative selection (artificial selection), in artificial selection it refers to where negative, rather than positive, traits of a species are selected for.

Negative selection (politics), is a process that occurs in rigid hierarchies, most notably dictatorships.

Negative selection (natural selection), in natural selection it refers to the selective removal of rare alleles that are deleterious.