The Heralds of Galactus are fictional characters appearing in comic books published by Marvel Comics. The Herald concept was introduced in Fantastic Four #48 (Mar. 1966) - with the character the Silver Surfer - by Stan Lee and Jack Kirby.
The entity Galactus maintains his existence by devouring planets that have the potential for supporting life, and as such utilizes a Herald to scour the universe in search of suitable worlds. Upon pinpointing the requisite planetary body, the Herald signals Galactus, resulting in his arrival on the world's surface followed by the deployment of the Elemental Converter — a colossal machine capable of draining all life energy from the planet within minutes. If the world in question supports a sentient civilization, the Herald will often be forced into battle with inhabitants who attempt to drive Galactus away.
This scenario resulted in the creation of what was at that time considered to be Galactus' first Herald, the Silver Surfer. Galactus spares the planet Zenn-La when Norrin Radd offers in exchange his services as a Herald. Galactus transforms Norrin Radd into the Surfer.
Since Galactus' first encounter with Earth, he has had a total of eleven Heralds.