Rinse the elderberries and remove any remaining stems or leaves.
Combine elderberries, water, and maple syrup in a small saucepan over medium heat.
Bring to a gentle simmer and cook for 8 to 10 minutes, stirring occasionally, until the berries burst and soften.
Remove from heat and mash with a fork or potato masher until mostly smooth, leaving a little texture.
Stir in the chia seeds and lemon juice until fully combined.
Let the jam cool at room temperature for 10 minutes, then spoon into a clean glass jar.
Refrigerate for at least 4 hours, or overnight, until the jam thickens to a spreadable consistency.