Fire Ore is a special type of ore found in Twinsy Tropics Dungeon in Mario & Luigi: Paper Jam. It was mined from the dungeons by kidnapped Toads, who were forced to mine the ore for Bowser and Paper Bowser in order to help build their Papercraft Bowser. Later, when Mario, Luigi and Paper Mario were in Neo Bowser Castle, the Bowser's unleashed their Papercraft Bowser on the trio, burning up the other four Papercrafts they used in previous battles. Afterwards, Toadette asks the trio to find three Fire Ores scattered around the castle to help her build her own Papercraft that could match the Papercraft Bowser.
While never directly stated, the Fire Ore appears to give certain structures abilities over fire, as shown by both Papercraft Bowser and Papercraft Fire Mario's abilities. While it was shown to give the Papercrafts fire abilities, it is unknown if the ore has similar effects to other beings.