'Sweet song';[6] published as The Perfect Nanny in the United States) is a 2016 novel by French author Leïla Slimani.

[8][7] Originally titled Chanson douce, it was translated as Lullaby for the UK and The Perfect Nanny in the US.

[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".

[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.