Using a vegetable peeler, remove 2 large strips of peel from the outset of the grapefruit being careful not to get the white pith under the grapefruit’s skin. Set peels aside.
In a small saucepan over medium heat, bring the water to a simmer. Combine sugar and hot water. stir until dissolved.
Remove from heat and add the 2 pieces of grapefruit peel. Let the peel infuse in the syrup until the syrup has reached room temperature.
Remove peels and refrigerate syrup until ready to use.
Grapefruit simple syrup will last in the refrigerator for up to 2 weeks.