Cuckoo Song is a children's or young adults' fantasy novel by Frances Hardinge, published on 8 May 2014 by Macmillan in the UK, and by Abrams Amulet in the USA.

Hardinge tells us that the name of The Grimmer, the pond Triss is rescued from, is taken from the name of a millpond in her grandmother's village, Wickham Skeith in Suffolk.

The character of Violet Parish is loosely based on her grandmother, who as a young woman shocked her home village by arriving there riding a motorcycle.

At home in Ellchester, she discovers a Besider delivering letters from her dead brother, Sebastian, who writes of being stuck in a perpetual winter.

The girls visit the Underbelly to meet the Shrike, who explains Triss's abduction was to punish her father for breaking an agreement with the Architect.

In December 2020 it was announced that Cuckoo Song would be adapted for Netflix by screenwriter Sarah Dollard.