Add the coarse coffee grounds to the bottom of your French press.
Pour cold or room-temperature water over the coffee grounds, making sure all grounds are fully wet.
Stir gently with a spoon to combine the coffee and water evenly.
Place the lid on the French press without pressing the plunger down. Let the coffee steep for 12 to 24 hours at room temperature or in the refrigerator.
After steeping, slowly press the plunger down to strain the coffee.
Pour the cold brew into a jar or bottle and store it in the refrigerator.
To serve, dilute with equal parts water or milk and pour over ice if desired.