Son Gohan is the first born son of Goku and Chi-Chi. Named after Goku's adoptive Grandpa Gohan. Gohan is the first Saiyan/Human hybrid, who are known as Halfbreeds. Despite Goku's protests Chi-Chi home schooled Gohan to be a scholar until he was four, before Goku took him to Kame Island to introduce him to Master Roshi, Bulma and Krillin. At this point he is a shy but very smart boy who also has a tail like Goku once had. But at the same time Goku's brother Raditz arrived and kidnapped Gohan. After being trapped in his space pod Raditz discovers Gohan has an even higher power level then Goku, this being the result of Gohan's emotions increasing his power.
During the battle between Goku, Raditz and Piccolo Gohan got angry and broke free of the space pod and delivered a devestating blow to Raditz, giving Goku and Piccolo time to kill him and Goku in the process.
Piccolo senses Gohan's power and takes him away for training, he left Gohan alone in the wilderness to survive against dinosaurs and other dangers for the good part of a year, Piccolo watching carefully. The rest of the year Piccolo taught Gohan how to fight, showing him no mercy. But soon Gohan's bright and cheerful nature made Piccolo protective over the young boy. When the time came for the Z Fighters to take on the remaining two Saiyans Vegeta and Nappa, Gohan held his own but at times his age caught up with him, making him frightened.
But when Nappa fired a lethal energy blast at Gohan, Piccolo threw himself in front of Gohan and took the impact. Piccolo died protecting Gohan, as the boy had given him a heart and was his true friend. Gohan was crushed at lost of his mentor and best friend. In anger he fired his trademark 'Masenko' blast at Nappa, which would have done heavy damage if it had not been blocked.
Later in the fight after Vegeta had beaten Goku, Gohan became an Oozaru and defeated Vegeta after landing on him.
Gohan chose to go to the planet Namek to gather the Namekian Dragonballs because when Piccolo died the Earth's Dragonballs were turned to stone. They planned on using the wishes to bring back their lost friends who died fighting the two evil Saiyans. Gohan was on a personal mission to wish back Piccolo and went so far as to wear a copy of Piccolo's Gi to honour him.
During the Namek saga Gohan proved to be a great warrior who might be one day stronger then his father.
After his father refused to return to Earth for the time being Gohan was sad and went back to his studies with resurrected Piccolo vowing to watch over him.
At the age of 7 Gohan trained with Piccolo and Goku (who had recently returned to Earth) for three years to fight Android 18 and Android 17, which Future Trunks had warned them about. He spent a further year with his father in the Hyperbolic Time Chamber, where he spent some quality time with his father whom he was rarely with.
At the age of 11 he emerged from the room as a Super Saiyan. At the Cell Games, to everyone's surprise Goku gave up after fighting Cell and chose Gohan to take his place. It was revealed that Gohan had a special power locked up inside him that came when he got really angry. These fits of power were very rare during his life. After Cell had his father and friends beaten by Cell Juniors, and had crushed peace loving Android 16's head, Gohan became the first to transform into Super Saiyan 2. He destroyed the Cell Jrs and could have easily beat Cell. But his cockiness let Cell prepare to self destruct, in order to blow up Earth. Goku teleported Cell away from Earth, killing himself in the process. Gohan was able to destroy Cell when he came back, but was scarred from the loss of his father. His victory over Cell was taken by Hercule, who would later play a big part in his life.
Seven years later and Gohan is now 18, now with a little brother called Goten. Chi-Chi decides Gohan needs to go to high school to finish his education. On his first day he turned Super Saiyan to stop a robbery and by the time he arrived at Orange Star High tales of the 'Gold Fighter' had already spread. In class he met the current crime stopper and the most popular girl in school, Videl. She is the daughter of Hercule, who got rich and famous for stealing Gohan's credit over the defeat of Cell. She is highly suspicious of Gohan and spies on him to see if he's the Gold Fighter. Gohan decides to use a disguise when fighting crime and goes to Bulma to make him a costume. He becomes the Great Saiyaman to hide his identify so that the media will not bother his family. He uses his powers to stop crime, something Videl doesn't like. She confronts Saiyaman and Gohan many times to voice her suspicions but Gohan nervously denies them.
But while saving an old dinosaur friend he reveals his identity accidentally to Videl who then blackmails Gohan to teach her to fly in exchange for her silence. Gohan, having no experience with kids his own age, especially girls is helpless against the confident Videl. She, like the rest of the world, believes her father is the strongest and he laid down a rule she was not allowed to date anyone unless they were stronger than him. During his training of Videl as well as his brother Goten, Videl learns more about Gohan and grows closer to him.
When Gohan suggested she cut her hair she blushed and asked him if he liked girls with short hair. But he explained that short hair was better for flying and fighting, at which she got mad and left, but came back the next day with short hair. After she learned to fly, she made Gohan agree to take part in the World Martial Arts Tournament, to which he agreed as his dad was coming back for that one day from Other World.
At the contest Krillin teased Gohan about Videl being his girlfriend, and Sharpner - a friend of theirs, was jealous and vowed to find out who Saiyaman was.
Later in the series, Gohan and Videl have a child, Pan.