Goku may have achieved the Super Saiyan transformation long ago, but that doesn’t mean he was the first to do so.
While the form was incredibly rare before Goku’s time, it wasn’t entirely unheard of. So, who else managed to attain it in Dragon Ball? Akira Toriyama answered this question years ago.
In an interview with Saikyou Jump, Akira Toriyama discussed various aspects of Dragon Ball and provided additional insights straight from the creator himself.
Yamoshi: The Original Super Saiyan
During the interview, Toriyama was asked whether the Legendary Super Saiyan, whom Vegeta feared, was the same as the Super Saiyan God introduced in the Battle of Gods movie. In response, the creator confirmed that both were indeed the same person.
The mangaka then delved into the story of Yamoshi, a warrior from an era long before the Saiyans ruled Planet Vegeta. Despite being a Saiyan, Yamoshi possessed a righteous heart.
He and his five comrades started a rebellion, but he was cornered by combatants and became a Super Saiyan for the first time, though his transformation and fearsome fighting style shocked the other Saiyans.
Unfortunately, Yamoshi was vastly outnumbered. Though he fought valiantly, exhaustion took its toll, and he was ultimately defeated. However, his fall marked only the beginning of his legend.
Afterwards, Yamoshi’s spirit wandered in continuous search of six righteous-hearted Saiyans, seeking a new savior: Super Saiyan God.

Toriyama also mentioned that Beerus became aware of Yamoshi through a prophetic dream. Additionally, the Namekian Book of Legends contains records of Yamoshi, likely because an elder Namekian who wrote it resonated with his spirit.
Why Were Frieza and Beerus Afraid of Yamoshi?
The idea that Goku wasn’t the first Saiyan to attain Super Saiyan is subtly hinted at by the reactions of Vegeta and Frieza. Vegeta, having been raised on Planet Vegeta, would have likely heard of the legend surrounding the first Super Saiyan.
Meanwhile, Frieza, known for his extensive knowledge of Saiyan history, may have come across information regarding Yamoshi.
Anyone would be shaken if a supposed legend became reality before their eyes. That likely explains Frieza’s reaction when he first witnessed the Super Saiyan form.
Given that Saiyan legends tend to glorify their warriors’ destructive power, Yamoshi’s strength must have been exaggerated over time. This could explain why Frieza, despite never encountering a Super Saiyan before, feared its existence.
Beerus and the Prophetic Dream
As for Beerus, his awareness of Yamoshi stemmed from a prophetic dream, through which he likely witnessed the warrior’s rage and desperation in battle. While Beerus may not have feared Yamoshi, he may have found him impressive enough to take notice.
You can read Dragon Ball on Viz Media and watch the anime on Crunchyroll.