In this form, the Saiyan's hair color differs, the same goes for the tail and the body is covered in red fur.

The form possesses all of the power of Golden Great Ape. The form's power is too great to be utilized by a child and so a child user is aged into an adult when using it. A user of this form loses some of their rationality. But for others, it can make them very cold and aggressive. This form gives the user the super strength and speed of a Great Ape, but with a calm, clever mind. It is possibly the Legendary Super Saiyan that appears once every 1,000 years. The form is a combination of the Super Saiyan and Great Ape forms attained through the Golden Great Ape form, it gifts the Saiyan with primal power, though they retain a humanoid appearance. The Super Saiyan 4 form was designed by Toei Animation's character designer Katsuyoshi Nakatsuru. In Dragon Ball Heroes Gohan acquired the form without a tail while training, and Xeno Trunks was originally going to have acquired the form too showing that even Half-Saiyans born without tails can still acquire Super Saiyan 4. Even after this form is attained, it cannot be accessed at will and requires exposure to Blutz Waves every time the user wishes to transform, however, Goku is apparently a special case, capable of using the form whenever he wishes. The only way a Saiyan can attain Super Saiyan 4 is if they have a high enough power level and become a Golden Great Ape (or Broly's variant) and regain conscious control over the form.

Gohan super sayayin 4