Combine the peaches and jalapeño in a large saucepan.
Stir in the sugar and water.
Bring the mixture to a boil over medium-high heat, then turn to a simmer.
Allow the peaches to simmer for 40-45 minutes, stirring constantly, until the mixture begins to break down. Use a potato masher to break up the larger pieces, if necessary
When the peaches begin to thicken and take on the consistency of a loose jam, remove from the heat.
Allow the jam to cool for 15-20 minutes before transferring to 2 pint jars and sealing with a lid.
Store in the refrigerator for up to 2 weeks.
