Sources where they first became available to players:
PHB = Player's Handbook
MM = Monsters Manual
MToF = Mordenkainen's Tome of Foes
SCAG = Swords Coast Adventurer's Guide
VGtM = Volo's Guide to Monsters
GGtR = Guildmasters' Guide to Ravnica
WGtE = Wayfinder's Guide to Eberron
DMG = Dungeon Master's Guide
EGtW = Explorer's Guide to Wildemount
Standard Languages:
- Common (PHB)
- Dwarvish (PHB)
- Elvish (PHB)
- Giant (PHB)
- Gnomish (PHB)
- Goblin (PHB)
- Halfling (PHB)
- Orc (PHB)
Standard Languages (Ravnica):
- Abyssal (PHB)
- Celestial (PHB)
- Common (PHB)
- Draconic (PHB)
- Elvish (PHB)
- Giant (PHB)
- Goblin (PHB)
- Kraul (GGtR)
- Loxodon (GGtR)
- Merfolk (GGtR)
- Minotaur (GGtR)
- Sphinx (MM)
- Sylvan (PHB)
- Vedalken (GGtR)
Exotic Languages:
- Abyssal (PHB)
- Celestial (PHB)
- Draconic (PHB)
- Deep Speech (PHB)
- Infernal (PHB)
- Primodial (PHB)
- Aquan
- Auran
- Ignan
- Terran
- Sylvan (PHB)
- Undercommon (PHB)
Race/Class-Specific Languages:
- Aarakocra (MM)
- Druidic (PHB)
- Gith (MToF)
- Thieves' Cant (PHB)
Forgotten Realms Human Languages (requires GM permission):
(All in SCAG)
- Dambrathan
- Bedine
- Alzhedo
- Chondathan
- Damaran
- Waelan
- Guran
- Halruaan
- Illuskan
- Roushoum
- Chessentan
- Mulhorandi
- Untheric
- Thayan
- Rashemi
- Shaaran
- Shou
- Tuigan
- Turmic
- Uluik
Eberron's Common Languages
- Common (PHB)
- Dwarvish (PHB)
- Elvish (PHB)
- Giant (PHB)
- Goblin (PHB)
- Orc (dead language, PHB)
- Infernal (PHB)
- Riedran (WGtE)
- Quori (WGtE)
- Blink Dog (MM)
- Bullywug (MM)
- Giant Eagle (MM)
- Giant Elk (MM)
- Giant Owl (MM)
- Gnoll (MM)
- Grell (MM)
- Grung (VGtM)
- Hook Horror (MM)
- Kruthik (MToF)
- Modron (MM)
- Otyugh (MM)
- Sahuagin (MM)
- Slaad (MM)
- Sphinx (MM)
- Thri-kreen (MM)
- Tlincalli (VGtM)
- Troglodyte (MM)
- Umber Hulk (MM)
- Vegepygmy (VGtM)
- Winter Wolf (MM)
- Worg (MM)
- Yeti (MM)
Book of Vile Darkness
Wildemount's common languages
- Zemnian (EGtW)
- Marquesian (EGtW)
- Naush (EGtW)