Stephen Hillenburg, a former marine biology teacher who created a children’s show that ballooned into an unlikely cultural phenomenon, “SpongeBob SquarePants,” died on Monday at his home in Southern California. He was 57.

Mr. Hillenburg announced last year that he had amyotrophic lateral sclerosis, the neurodegenerative condition known as Lou Gehrig’s disease. Nickelodeon, the channel that has been the show’s home since its premiere in May 1999, announced his death.

“Steve imbued ‘SpongeBob SquarePants’ with a unique sense of humor and innocence that has brought joy to generations of kids and families everywhere,” the network said in its statement. “His utterly original characters and the world of Bikini Bottom will long stand as a reminder of the value of optimism, friendship and the limitless power of imagination.”

Bikini Bottom is the underwater home of the show’s title character, a good-natured yellow kitchen sponge, or sea creature, or both, who works as a fry cook, has a pet snail and lives in a pineapple.