Cut the watermelon into manageable chunks, removing the rind if necessary, and place them into the blender.
Add a squeeze of fresh lime juice if desired for a tangy twist.
Cover the blender with its lid and blend on high until the watermelon is completely smooth and frothy, about 30 seconds.
If you prefer a seed-free juice, strain the blended mixture through a fine mesh strainer into a large pitcher, pressing gently to extract as much liquid as possible.
Pour the fresh watermelon juice into glasses, and serve immediately over ice if desired for extra refreshment.
Enjoy the cool, invigorating flavor of homemade watermelon juice, perfect for hot days or a quick fruity refresh.