Steve Fox (スティーブ・フォックス Stību Fokkusu?) is a character in the Tekken series, first appearing in Tekken 4, he has returned for all subsequent games. Steve is a young British boxer who was adopted at a young age and whose origins long remained shrouded in mystery. Throughout the games, Steve's main objective has been to learn more information about his past, including the origin of the mysterious scar on his arm, and to get revenge against those responsible.

With his debut in Tekken 4, it was revealed that he is the biological son of Nina Williams and that his conception was done synthetically by the Mishima Zaibatsu. Then later in Tekken Tag Tournament 2 and Tekken 7, it was revealed that the Zaibatsu ordered his conception in order to get themselves a new, more durable, test subject for their experiments. After reclaiming the Mishima Zaibatsu from his son and witnessing the power of the Devil firsthand in the second King of Iron Fist Tournament, CEO Heihachi Mishima began his own research into the terrifying power of the Devil Gene.

What was found out, was that the Devil Gene only appeared naturally on rare individuals and could grant its owners an immense boost in power by instantaneously activating the body's own cells. Trying to replicate this superhuman strength, the Mishima Zaibatsu started a genetic modification plan with the goal to replicate the effects of the gene on regular humans. These treatments would prove to be extremely demanding, however, and would lead to the deaths of multiple test subjects.

To combat this, Heihachi ordered the synthetic creation of a specimen capable of withstanding the treatments using the egg of assassin Nina Williams, who was cryogenically frozen by Dr. Bosconovitch and the Zaibatsu at the time, and the seed of an unknown father. For the next six years, this specimen, only dubbed as NT01, would be used as a test subject for the Zaibatsu's gruelling experiments.

During this time, however, one of the project's supervisors, Emma Kliesen, against the wishes of her colleagues, developed a bond with the boy, possibly also giving him the name Steve. It was also Emma who helped Steve escape the laboratories at the age of 6 by faking his death in an experiment. After this, Steve was most likely brought to an orphanage and was adopted by British parents, earning him his nationality and accent later in life.

It is unknown to what extent, if any, the experiments done in his childhood affected his physical capabilities, but what is known, is that 15 years later, Steve Fox would be known as one of the world's best middleweight boxing champions. Steve himself, however, would end up remembering next to nothing about his past before his adoption. After an incident with the mafia, Steve entered the fourth tournament and found out during it that he was going to be assassinated by Nina Williams; fortunately, this did not happen due to Nina having a rare moment of emotion. He entered the fifth tournament to "settle the score" with the Mishima Zaibatsu.

Steve Fox has had plenty of run-ins with the Mishima Zaibatsu, but he never gave up his search for information about his past. Though his mother's identity remained a mystery, one name, in particular, began to crop up time and again: Nina Williams. Believing she knew something, Steve began investigating her whereabouts until he came up with a promising lead.

The information led him to an imposing cathedral. As he considered how best to proceed, a figure appeared from inside, dressed in a tattered wedding gown. It was Nina, who seemed to be running away from something. Steve told her to stop, but she ignored him and fled. Determined not to let this opportunity escape him, he blocked her path.

Ending Description: After defeating Nina, Steve tells her of all that he knew of his past and demands to know how she is connected to him. She explains to him that her genes were used by the Mishima Zaibatsu to create ultimate supersoldiers through experimenting on children, with Steve as one of them. The project failed due to most of the children dying from that experiment, but Steve survived thanks to Emma Kliesen's efforts to cover up Steve's status from the Zaibatsu's eye. As Steve discovers that she is his mother, Nina warns him that he will never be her son because she couldn't care less about him. When the Tekken Force suddenly arrives, Steve helps Nina escape while holding them off.