Formal/poetic:
* Âme sœur (literally "soul sister") - This is the most common translation, but it can sound a bit formal and old-fashioned.
* Double flamme (literally "double flame") - This is a more romantic and modern translation, implying a strong connection and shared destiny.
* Âme jumelle (literally "twin soul") - This suggests a strong connection and compatibility, but it can also be interpreted as a platonic relationship.
Informal/colloquial:
* La moitié de mon âme (literally "half of my soul") - This expresses a deep connection and dependence on the other person.
* L'amour de ma vie (literally "the love of my life") - This is a more general expression of love, but it can also convey the idea of a soulmate.
Other options:
* Allié de l'âme (literally "soul ally") - This implies a connection based on shared values and goals.
* Destiné (literally "destined") - This suggests that the relationship is meant to be.
Ultimately, the best translation will depend on the specific context and your personal interpretation of "soul mate."