From Lexicanum

A δ-class (delta class) or Dead World is an airless and completely sterile world, totally devoid of an atmosphere, ecosystem and native natural life, and unsuitable for supporting any. With the possible exception of Imperial facilities such as Research Stations based on the planet, its population is otherwise nonexistent.

Most such planets have always been dead worlds; others were originally habitable worlds, reduced to dead world status through apocalyptic events, such as exterminatus, Tyranid consumption and destructive internecine war.

A dead world's tithe grade is aptus non ("not applicable").¹

Notable Dead Worlds

Planet name	Segmentum	Sector	Subsector	System	Population
Adrantis Five	Segmentum Pacificus	Unknown	Unknown	Unknown	N/A
Belis Corona	Segmentum Obscurus	Belis Corona	Belis Corona	Belis Corona	Unknown
Berien VI	Ultima Segmentum	Unknown	Unknown	Unknown	Unknown
Doton	Ultima Segmentum	Unknown	Unknown	Unknown	Unknown
Dunen II	Ultima Segmentum	Unknown	Unknown	Unknown	Unknown
El'Phanor	Segmentum Solar	Unknown	Unknown	Unknown	N/A
Evangel	Ultima Segmentum	Unknown	Unknown	Unknown	Unknown
Gryphonne IV	Segmentum Tempestus	Unknown	Unknown	Unknown	8,520,000,000/0
Holda	Ultima Segmentum	Unknown	Unknown	Unknown	Unknown
Isstvan III	Unknown	Unknown	Unknown	Unknown	N/A, was 12 billion pre-Heresy2,3
Naogeddon	Unknown	Unknown	Unknown	Unknown	Unknown
Olympia	Unknown	Unknown	Unknown	Unknown	Unknown
Prandium	Ultima Segmentum	Ultramar	Unknown	Unknown	N/A
Truan IX	Unknown	Unknown	Unknown	Unknown	Unknown
Tyran	Eastern Fringe	Unknown	Unknown	Unknown	N/A
Valos	Ultima Segmentum	Unknown	Unknown	Unknown	N/A
Zhoros	Unknown	Unknown	Unknown	Unknown	Unknown

Sources

• ¹: Warhammer 40,000 3rd Edition Rulebook p.115

Worlds of the Galaxy

Imperium	Adeptus Astartes Homeworld • Agri World • Cardinal World • Civilised World • Dead World • Death World • Desert World • Feral World • Feudal World • Forge World • Hive World • Ice World • Industrial World • Jungle World • Knight World • Mining World • Ocean World • Paradise World • Penal World • Research Station • Shrine World
Xeno	Xenos World • Daemon World • Exodite World • Tomb World • Maiden World • Crone World • Ork World • Tau Empire • Craftworld