Old Reliable is a geyser in the fictional Kookamunga National Park, in the animated children's TV series Iggy Arbuckle. It's name and routine eruptions are a parody of the geyser Old Faithful, in Yellowstone National Park, Wyoming, USA.

The geyser erupts on a daily basis, and is used by the residents of the Kookamunga as a "natural" laundromat. The episode "I Fought the Laundromat" focuses largely on this; Catfish Stu blocks off the flow of the water which would usually be erupted by the geyser, so that the townspeople will have to stop using the geyser for their laundry, and resort to his new laundromat. Iggy and Jiggers discover his plans, and upon explaining to him the dangers of blocking the water off of its natural course, and observing some of these taking place, they set about and correct the problem. The townspeople keep a sign containing photographs depicting different eras of civilization in the Kookamunga, who used the geyser for this purpose. Interestingly, some of these photographs show people from times before cameras existed, most notably one depicting an early paleolithic tribe.

Old Reliable is not the only named geyser in the Kookamunga, as in "Any Friend of Yours", Iggy briefly mentions another one called the Geezer Geyser.