Cut the watermelon into cubes and remove any black seeds if you are using a watermelon that isn't seedless. Add the watermelon to a high powered blender or food processor.
Add the lime juice and zest to the blender or food processor, followed by the mint leaves. Blend until smooth.
Pour into a freezer-safe container, cover and freeze for at least 4 hours before scooping and serving.
Notes
Nutritional facts do not include sugar, as it is optional. Serving size is for ½ cup of sorbet.