Lullaby (French: Chanson douce, lit. 'Sweet song';^[6] published as The Perfect Nanny in the United States) is a 2016 novel by French author Leïla Slimani.

The book deals with the murder of two children by their nanny.^[7] It was inspired by the real-life 2012 murder of children by their nanny in New York.^[8][9]

Lullaby is Slimani's second novel^[8] and the first to be translated into English.^[10] By January 2018 it had been translated into 18 languages, with intentions for a further 17.^[8][7] Originally titled Chanson douce, it was translated as Lullaby for the UK and The Perfect Nanny in the US.^[8]

It sold 600,000 copies in France in its first year of publication.^[8]

Lullaby was described by Aida Edemariam (writing in The Guardian) as "stylishly written [...] brilliantly executed".^[10] It was compared to Gone Girl by both Celia Walden of The Telegraph^[9] and Lucy Scholes of The Independent, with the latter describing it as "a psychological thriller that will have readers on the edge of their seats".^[12]

The novel won the 2016 Prix Goncourt, a top French literary award.^[13]

In 2019, a film adaptation, of the same name in certain countries and entitled Perfect Nanny in some others, was made by director Lucie Borleteau, starring Karin Viard, Leïla Bekhti and Antoine Reinartz.^[14]

In January 2023, it was reported that a planned television limited series adaptation entitled The Perfect Nanny was in development at HBO with Legendary Television co-producing. Nicole Kidman and Maya Erskine are set to star.^[15]