Your mother tongue ( also mother-tongue) is the language that you learn from your parents when you are a baby.

Example:

In a May 2019 survey, about a third of Ukrainians named Russian as their mother tongue.

And as an added bonus, native English speakers will be able to speak in their mother tongue.

But most also want their children to gain a strong grounding in their mother tongue first.

There’s one final touch: stapled onto each bag is a note written in the mother tongue of the person who will receive it.

Half the world’s population speaks a language that has evolved from a single, prehistoric mother tongue.

Tradução: língua materna, língua nativa.