Add the rhubarb, sugar and water to a small pot and place over a medium/low heat. Bring nearly to the boil, then reduce the heat and simmer for 20 minutes.
Allow the rhubarb syrup to cool slightly, then strain through a fine mesh strainer over a bowl.
Tip: Save the rhubarb solids - they’re like a sweet compote and great on yogurt or ice cream.
Pour the simple syrup into a bottle or jar and store in the fridge for up to 2 weeks.