In a saucepan, combine raspberries, sugar, and water.
Bring the mixture to a boil over medium heat, stirring occasionally.
Once it reaches a boil, reduce the heat to low and simmer for 10-15 minutes, mashing the raspberries with a spoon as they soften.
Remove the saucepan from heat and let the syrup cool.
Strain the syrup through a fine-mesh sieve into a clean container, pressing on the solids to extract all the liquid.
Discard the remaining solids and refrigerate the syrup until ready to use
Refrigerate in an airtight container for up to three weeks.