All-speak
This is considerable debate in magical circles as to whether All-Speak is a magical language in its own right which is mutually intelligeble with most other languages, or whether users of All-Speak are speaking their own native language and this is being translated by a passive magical ability.
Because the Aesir use All-Speak as their primary means of communication, it is unclear whether an Asgardian language exists or not. Proponents of the All-Speak as an ability theory point to cultural terms which are translated inexactly (the terms translated by All-Speak to English as North and South, for example, are more accurately undestood as 'towards the light' and 'towards the dark', as the Aesir do not use magnetic north in navigation) and the the fact that written Asgardian runes are not translated the way spoken language is as evidence that the Aesir are actually speaking a native Asgardian language, rather than actually speaking All-Speak.
One fringe theory has possited that there is no single Asgardian language, and that every Aesir speaks their own invented language which would be nonsense to even other Aesir, but since all Aesir use the All-Speak this is not apparent.
In addition to the Aesir, the Vanir and Giants are typically raised to use All-Speak as their primary means of communication from birth, but other magical species are capable of using it. Light Elves use it as a lingua franca, due to the variation in dialects in their native language. Trolls, Dwarves and Dark Elves have been known to use it, although it is not a common skill in any of their cultures. Of the inhabitants of the Nine Realms, only Humans and Inhumans have shown no aptitude for All-Speak.
Some languages are incompatible with All-Speak, such as Groot.