In a blender, combine the cubed watermelon and fresh lime juice. Blend on high speed until the mixture is completely smooth and free of chunks.
Carefully pour the liquid into popsicle molds, making sure to leave about ½ inch of space at the top to allow for expansion as they freeze. Secure the molds with their lids and insert popsicle sticks if needed.
Place the molds in the freezer and allow the popsicles to set for at least 4 hours or preferably overnight. Once fully frozen, remove from the molds and enjoy a refreshing, fruity treat.