Ama, more commonly known as Doraemon, is a male cat-type robot from the 22nd century. He was manufactured on September 3, 2112, in a factory that mass-produces robotic cats. Due to an accident on the production line, he lost a single screw, which classified him as a defective or "seconds" product compared to his peers. He was purchased from a department store's bargain bin by a boy named Sewashi, who is the descendant of the main character, Nobita Nobi. Sewashi sent Doraemon back in time to the 20th century to care for his ancestor, Nobita, and help improve the fortunes of the Nobi family, which had become impoverished due to Nobita's laziness and lack of success.

Physically, Doraemon has a distinctive appearance. He has a large, round, blue body with a white belly and hands. Originally, he was orange and had ears, but after a robot mouse bit them off, he cried so profusely that the tears washed away his yellow paint, leaving the blue undercoat exposed. His specifications are almost exclusively tied to the number 129.3, representing his height in centimeters, his weight in kilograms, and his chest measurement, which is a reference to the average height of a Japanese fourth-grade student when the manga was first published. His most famous feature is the fourth-dimensional pocket on his abdomen, from which he can produce a vast array of futuristic gadgets and tools. Other notable features include infrared eyes for seeing in the dark, a powerful nose that is now broken, a mouth large enough to hold a washbasin, radar whiskers that also no longer function, a bell that was meant to summon cats, and a flat, spherical tail that serves as his master switch; pulling it completely shuts down his systems.

Doraemon's personality is defined by his kind and caring nature, though he is often portrayed as a well-meaning bungler. He has a strong sense of responsibility toward his mission of helping Nobita, but he is also quick to lose his temper or become emotional, especially when he is mistaken for a raccoon dog or when confronted with his two greatest fears: mice and the cold. His genuine love for food, particularly the sweet red bean paste-filled confection known as dorayaki, is a defining character trait. While he is a highly advanced robot, he displays many human-like qualities, including a fondness for pretty female cats, whom he often attempts to impress, and a tendency to act lazy or selfish at times, providing a humorous contrast to his role as a moral guide.

Doraemon's primary motivation is to change Nobita's future for the better. He was sent from the 22nd century with the specific directive to help Nobita overcome his weaknesses, such as his poor grades, lack of athleticism, and tendency to be bullied by his classmates, Takeshi "Giant" Goda and Suneo Honekawa. Although he constantly lectures Nobita about relying on his own effort and not abusing future technology, Doraemon almost always gives in to Nobita's desperate pleas and provides a gadget from his pocket. This dynamic forms the core of the story, with Doraemon's willingness to help and Nobita's frequent misuse of the tools often creating complicated situations that they must then resolve.

His role in the narrative is that of a guardian, mentor, and best friend to Nobita. He is the catalyst for the story's adventures, providing the means for time travel, undersea exploration, and journeys to distant planets. Beyond his relationship with Nobita, Doraemon interacts closely with other main characters. He has a cordial but often exasperated relationship with Nobita's mother, Tamako, who is unaware of his true origins. He is friends with Nobita's kinder classmate, Shizuka Minamoto, who often appreciates his help. He also has a sister, Dorami, who is a superior and more responsible robot and is sometimes sent to check on him. Despite his status as a defective model, Doraemon is a loyal and steadfast companion, and his presence is the driving force behind the group's many adventures.