Gather the ingredients.

Combine rhubarb, sugar, water, orange juice, and orange zest in a saucepan over high heat; bring to a boil. Reduce heat to medium-low; cook, stirring occasionally, until thick, about 45 minutes. Jam will continue to thicken as it cools.

Sterilize the jars and lids in boiling water for at least 5 minutes. Use a jelly funnel and soup ladle to pack jam into hot, sterilized jars, filling to within 1/4 inch of the top. Run a knife or thin spatula around the insides of the jars to remove any air bubbles. Wipe the rims with a moist paper towel to remove any food residue. Top with lids and screw rings on tightly.

Place a rack in the bottom of a large stockpot and fill halfway with water. Bring to a boil over high heat, then carefully lower the jars into the pot using a holder. Leave a 2-inch space between the jars. Pour in more boiling water to cover jars by at least 1 inch. Bring to a rolling boil, cover, and process for 5 minutes.