The Infanticide Act is the name for a number of laws introduced into UK law (England and Wales, Scotland and Northern Ireland) that recognised the special nature of the killing of an infant child by its mother during the early months of life.

The dates given here are for the legislation applying in England and Wales.

The Infanticide Act, 1922 effectively abolished the death penalty for a woman who deliberately killed her new born child while the balance of her mind was disturbed as a result of giving birth, by providing a partial defence to murder. The sentence that applies (as in other partial defences to murder) is the same as that for manslaughter.

The Infanticide Act, 1938 extended this defence to cases where "at the time of the act or omission the balance of her mind was disturbed by reason of her not having fully recovered from the effect of giving birth to the child or by reason of the effect of lactation consequent upon the birth of the child."

Before the partial murder defence of Diminished responsibility was introduced to UK law in 1957, this provided an important means of selecting a more appropriate sentence for a mother found guilty of killing her infant than the mandatory life sentence or death sentence applying to murder at the time.

In recent years it has become very rare for a mother who kills her infant child to receive a custodial sentence, save in very exceptional circumstances.