The so-called Heart Book (Hjertebog, Copenhagen, Kongelige Bibliotek, Thott 1510, 4º) is a 16th-century Danish manuscript (Thott 1510 4o), now kept in Det Kongelige Bibliotek, Copenhagen.
It is a collection of 83 Danish love ballads, collected in the 1550s at the court of king Christian III. It is the oldest known Danish ballad manuscript.
A peculiarity of the manuscript the entire book is heart shaped, in one of the early examples of the heart shape being used to signify romantic love.