The planes of the Dungeons & Dragons roleplaying game constitute the multiverse in which the game takes place.
In the earliest versions of Dungeons & Dragons, the concept of the Inner, Ethereal, Prime Material, Astral, and Outer Planes was introduced; at the time there were only four Inner Planes and no set number of Outer Planes. This later evolved into the Great Wheel cosmology. The fourth edition of the game used a different, very simplified cosmology with just six main planes called the World Axis Cosmology. The fifth edition has brought back a new version of the Great Wheel cosmology.
In addition, some Dungeons & Dragons settings have cosmologies that are very different from the "standard" ones discussed here. For example, the Eberron setting has only seventeen planes in total, most of which are unique to Eberron.
This standardized layout of the planes was presented for the first time in Volume 1, Number 8 of The Dragon, released July 1977. The known planes of existence were presented again in an appendix in the original (1st edition) AD&D Players Handbook, published in June 1978. The planes were expanded upon in the original Manual of the Planes, released in 1987. It was the core cosmology in both editions of AD&D and the 3rd and 3.5 editions of D&D.
Well my mind has been overflowin'
'bout some things that don't seem right.
And my gun is cocked and loaded,
I hope I get me some sleep tonight.
Well I don't know what went wrong,
It seems like nuthin' is right.
Well I don't know what went wrong,
I hope I get me some sleep tonight.
So take it nice and easy,
Leave the coals in the pit.
Don't let your mind post-toastee,
Like a lot of my friends did.
Just keep me out of L.A.,
Things are crazy out there.
From people that I been meetin',