Put water, sugar, and cranberries in a medium saucepan and bring to a boil.
Once boiling, lower heat and let mixture simmer for about 10 minutes until cranberries have burst and mixture has thickened.
Strain mixture into a bowl, pressing down on the cranberries with a wooden spoon or spatula to extract as much juice as possible.
Keep syrup in bowl or pour into a mason jar and place in fridge to cool completely before using. Syrup will continue to thicken as it cools.