Combine raspberries, sugar, and water in a saucepan.
Bring to a boil over medium heat, stirring until the sugar dissolves.
Reduce heat and simmer for 5-7 minutes, allowing the raspberries to break down.
Remove from heat and let steep for another 5 minutes.
Strain the syrup through a fine-mesh sieve into a clean jar or bottle, pressing down on the solids to extract as much liquid as possible. Discard the solids.
Let the syrup cool completely before sealing and storing in the refrigerator.
Notes
Store in an airtight container in the refrigerator for up to 2 weeks.