This section shows a selection of Space Marine Chapters that are, or have been at some stage during their existence, described as Codex Chapters. Some of these Chapters are venerable orders having a history that dates back to the dawn of the Imperium, others are more recent additions to the ranks of the Adeptus Astartes. This selection is by no means a complete record of all the Codex Chapters. Even though there are relatively few Codex Chapters amongst the thousand or so Chapters currently active across the Imperium some Imperial scholars reckon there to be well over a hundred of them and there may be as many as two to three hundred in truth.

The term 'Codex Chapter' is not an official Imperial name for these regiments but over the millennia it has become a common way of describing a Chapter that follows the teachings and traditions of Robute Guillimaris Codex Astartes. Some of these Chapters have always followed the rules laid down in the great book, the Ultramarines Chapter being the most obvious example. Other Chapters may have followed the prescriptions of the Codex for a period and then devolved to some system of their own devising. In some cases Chapters have taken to the Codex later in life having previously followed some other system of organisation and heraldry. This is particularly common if a Chapter has been all but annihilated and has had to have been subsequently rebuilt.

Each of the examples illustrated shows a brother-marine of the 3rd Squad (Tactical), 2nd Company. This makes it simple to compare the different Chapters and to work out details of other Squads and Companies by simply cross-referencing with the Ultramarines information presented elsewhere in this book. Where appropriate the individual diagrams have notes highlighting significant variations from the Ultramarines heraldry.