Closest to "soulmate":
* Âme sœur (f): This literally means "soul sister" and is the closest translation to "soulmate."
* Double (m/f): This translates to "double" and implies a sense of being two halves of the same whole, a very strong connection.
* Moitié (f): This means "half" and suggests that someone completes you, like the other half of a whole.
Other possibilities:
* Amour de (one's) vie (m/f): This literally means "love of one's life" and implies a very deep and enduring love.
* Destin (m): This means "destiny" and implies that your paths were meant to cross.
Note: The closest equivalent to "soulmate" in French is a concept that's often expressed through metaphor, like saying someone is your other half or your other self.
Ultimately, the best translation will depend on the context and the specific meaning you want to convey.