Order is primarily opposed to Chaos, and its factions are united by a common desire to maintain civilisation, art, and learning, or preserve natural or divine holdings.
Despite this shared goal, each faction more or less pursues its own agenda - sometimes to the detriment of the others.

Stormcast Eternals, demigod-like warriors imbued with a portion of Sigmar's godly power and clad in magical armour made of sigmarite, analogous to the Space Marines of Warhammer 40,000.
They were created by Sigmar with the aid of Grungni to be the ultimate weapon against the forces of Chaos.

Cities of Sigmar, the cities established by the forces of Order, they represent the everyday citizens of the Mortal Realms.
The majority of the dwarf, elf, and human units from Warhammer Fantasy that continued into Age of Sigmar make up the bulk this army.
While they are all the same army, each unit has a species keyword and each species is divided into several subfactions, with leaders' spells and abilities synergising with particular keywords, allowing for the armies to be played as diverse or similarly to how they played in Warhammer Fantasy.
Stormcast Eternals are also able to be taken by all cities without regard to normal point limits on allies but may only make up 1/4 of the units in the army while the Living City is able to do the same with Sylvaneth and Tempest's Eye with the Kharadron Overlords.

Duardin, previously the Dwarfs.
The Dispossessed represent the more traditional Dwarfs who still bear grudges against their enemies and worship Grungni.
The Ironweld Arsenal focuses on the artillery element of the Dwarfs and are allied with humans.

Humans include the Devoted of Sigmar, priests and evangelists, the wizards of the Collegiate Arcane, and the Freeguild knights, archers, and soldiers.

Aelfs, previously the Elves.
These include the Wanderers, the wizards of the Eldritch Council, the warriors of the Phoenix Temple, the Lion Rangers, the Swifthawk Agents, the Orders Draconis and Serpentis, the fleets of the Scourge Privateers, the warlocks of the Darkling Covens, and the Shadowblade assassins.

Seraphon, previously the Lizardmen.
In the current iteration they are celestial Daemons who fight for Order.
The Slann, now aboard great cosmic vessels, literally "remember" the seraphon into existence whenever needed although at least some of the temple-ships still have spawning pools that produce them in the same manner as they originally were in Warhammer Fantasy.

Sylvaneth forest spirits range from dryads to towering treelords, and follow the reborn goddess Alarielle.

Fyreslayers are mercenary duardin who worship Grimnir and fight for Ur-Gold, a magical element believed to be remnants of their fallen god.

Kharadron Overlords are a steampunk duardin faction that consists of ironclad airships and warriors wearing armoured suits.
Separated a long time ago from the rest of their race, the Kharadron live in sky-cities and are armed with shooting weapons powered by aether-gold.

The Daughters of Khaine are a shadowy cabal of witch aelves devoted to Khaine and Morathi; ostensibly they wish to revive Khaine, but Morathi secretly is plotting to ascend to godhood.

The Idoneth Deepkin are marine aelves created by Teclis (the aelven Mage God) that ride sea monsters into battle and raid for souls on the surface.

The Lumineth Realm-lords are aelves from the realm of Hysh (the realm of Light), and are the second and successful attempt by Teclis to recreate the Asur aelves from the world-that-was.
Order is primarily opposed to Chaos, and its factions are united by a common desire to maintain civilisation, art, and learning, or preserve natural or divine holdings. Despite this shared goal, each faction more or less pursues its own agenda - sometimes to the detriment of the others.
Stormcast Eternals, demigod-like warriors imbued with a portion of Sigmar's godly power and clad in magical armour made of sigmarite, analogous to the Space Marines of Warhammer 40,000. They were created by Sigmar with the aid of Grungni to be the ultimate weapon against the forces of Chaos.
Cities of Sigmar, the cities established by the forces of Order, they represent the everyday citizens of the Mortal Realms. The majority of the dwarf, elf, and human units from Warhammer Fantasy that continued into Age of Sigmar make up the bulk this army. While they are all the same army, each unit has a species keyword and each species is divided into several subfactions, with leaders' spells and abilities synergising with particular keywords, allowing for the armies to be played as diverse or similarly to how they played in Warhammer Fantasy. Stormcast Eternals are also able to be taken by all cities without regard to normal point limits on allies but may only make up 1/4 of the units in the army while the Living City is able to do the same with Sylvaneth and Tempest's Eye with the Kharadron Overlords.
Duardin, previously the Dwarfs. The Dispossessed represent the more traditional Dwarfs who still bear grudges against their enemies and worship Grungni. The Ironweld Arsenal focuses on the artillery element of the Dwarfs and are allied with humans.
Humans include the Devoted of Sigmar, priests and evangelists, the wizards of the Collegiate Arcane, and the Freeguild knights, archers, and soldiers.
Aelfs, previously the Elves. These include the Wanderers, the wizards of the Eldritch Council, the warriors of the Phoenix Temple, the Lion Rangers, the Swifthawk Agents, the Orders Draconis and Serpentis, the fleets of the Scourge Privateers, the warlocks of the Darkling Covens, and the Shadowblade assassins.
Seraphon, previously the Lizardmen. In the current iteration they are celestial Daemons who fight for Order. The Slann, now aboard great cosmic vessels, literally "remember" the seraphon into existence whenever needed although at least some of the temple-ships still have spawning pools that produce them in the same manner as they originally were in Warhammer Fantasy.
Sylvaneth forest spirits range from dryads to towering treelords, and follow the reborn goddess Alarielle.
Fyreslayers are mercenary duardin who worship Grimnir and fight for Ur-Gold, a magical element believed to be remnants of their fallen god.
Kharadron Overlords are a steampunk duardin faction that consists of ironclad airships and warriors wearing armoured suits. Separated a long time ago from the rest of their race, the Kharadron live in sky-cities and are armed with shooting weapons powered by aether-gold.
The Daughters of Khaine are a shadowy cabal of witch aelves devoted to Khaine and Morathi; ostensibly they wish to revive Khaine, but Morathi secretly is plotting to ascend to godhood.
The Idoneth Deepkin are marine aelves created by Teclis (the aelven Mage God) that ride sea monsters into battle and raid for souls on the surface.
The Lumineth Realm-lords are aelves from the realm of Hysh (the realm of Light), and are the second and successful attempt by Teclis to recreate the Asur aelves from the world-that-was.
Warhammer Age of Sigmar