In a large bowl, toss watermelon cubes with lemon juice and fresh mint.
Refrigerate until ready to serve. The longer this sits, the better it gets! Serve cold.
Notes
If you'd like to add Feta Cheese (a classic addition), sprinkle in 1/2-1 cup of crumbled feta before serving. It adds a creamy, salty bite that is delicious with a bite of cold watermelon.