This is a list of the known realms of Arda in J. R. R. Tolkien's legendarium. Major locations within realms, if any, are listed under each. Dates given in brackets refer to the fictional timeline of Arda.
Erebor
Moria
Nogrod
Belegost
Angband
Hithlum (founded c. 1)
Dor-lómin (founded c. 1, given to Men c. 400)
Nevrast (founded c. 1, until 104)
Nargothrond (founded c. 50)
Dorthonion (founded c. 1)
Tol Sirion (founded c. 1)
Gondolin (founded c. 64)
March of Maedhros (founded c. 1)
East Beleriand (founded c. 1)
Himlad (founded c. 1)
Thargelion (founded c. 1)
Maglor's Gap (founded c.1)
Falas (destroyed 473)
Eglador, later Doriath
Avarin and Nandorin realms
Lórinand
Ossiriand
Dorwinion
Nan Elmoth
Tol Eressëa
Estolad (until c. 450)
Dor-lómin (inhabited by men c. 400)
Brethil (after c. 400)
Ladros (after c. 400)
Forests of Eriador
Fangorn forest
Forests of South Beleriand
Aman
Arda The Realm
Valinor
Númenor (founded 32, destroyed 3319)
Lond Daer originally Vinyalondë (foresting colony, founded c. 1000)
Arnor (first colonized c. 800, founded 3320 by Elendil)
Gondor (first colonized c. 1100, founded 3320 by Elendil)
Umbar (first colonized c. 1100, founded c. 3220 by Black Númenóreans)
"Dead Men" of the White Mountains
Men of the First and Third Houses in Eriador (merged with Arnor)
Men of the Second House in Enedwaith and Minhiriath (later Dunlendings)
Drúedain of Drúwaith Iaur and Drúadan Forest
Lossoth of Forodwaith
Avarin and Nandorin realms
Lórinand (after c. 1400 Lothlórien)
Edhellond (southern 'colony' of Lórinand)
Eregion (until 1697)
Lindon
Greenwood the Great (of Oropher)
Dúnedain and allies
Gondor
Dol Amroth (de facto independent realm)
Umbar (943–1447 and 1810–1944 only)
Arnor (divided 861)
Arthedain (until 1975)
Cardolan (until c. 1410)
Rhudaur (until 1409)
Kingdom of Rhovanion (until 1851)
Éothéod (until 2510), afterwards:
Rohan
Dale and Esgaroth (c. 2940 onwards)
Bree-land (shared with Hobbits)
Dunland
Harad
Umbar (until 943, 1447–1810 and 1944 onwards Corsairs of Umbar)
Khand
Rhûn
Forodwaith
Noldorin, Sindarin, and Sindarized Nandorin realms
Lindon
Lothlórien
Northern Mirkwood (of Thranduil)
Rivendell
Gladden Fields
The Shire
Bree-land (shared with Men)
Buckland
Fangorn forest and possibly the Old Forest
Reunited Kingdom of Gondor and Arnor
Containing within it, the autonomous realms of:
Drúadan Forest (Drúedain)
The Shire (Hobbits)
Treegarth of Orthanc (Ents)
Rohan
Harad
Khand
Rhûn
Núrnen
Dale and Esgaroth
Dorwinion
Greenwood the Great
Lórien on both sides of Anduin
Elves of Ithilien
Remnant of Lindon
Realms of Arda Wikipedia (Text) CC BY-SA