The main star of Dragon Ball's ever-continuing franchise is popularly known for his countless forms that he introduces in the many continuations of the show. From the very first Kaio-ken that Goku learned from King Kai, to the newest Mastered Ultra-instinct, Goku has mastered plenty of different transformations to use against his opponents when necessary.
For obvious reasons, these transformations always tend to get stronger and more flashy as the show goes on, with hair changes and bright colors. Guessing which form is to come next is as easy as picking a new hair color that Goku would sport. Of the many aspects of each transformation, strength is the most important. The boost in strength is how Goku bests his enemies, after all.
14 Great Ape
As just a small child, Goku was able to reach his first transformation. Unfortunately, he didn't achieve it purposefully, for when Saiyans, who still have their tail, are under a full moon, they begin to transform into a Great-Ape. In this form, Goku is monstrously large, and his power is extreme, yet uncontrollable.
Great-Ape Goku would've been a problem for the planet in his childhood, as his power level was multiplied. With strength, ki, and vitality that surpassed any other combatant in his Dragon Ball days, Great-Ape was a horrifying force to be reckoned with.
13 False Super Saiyan
Though the Lord Slug movie isn't exactly canon, fans got a glimpse at what Super Saiyan would look like before they ever saw it hit Dragon Ball Z in the fight with Frieza. Goku is seen going up against Lord Slug, and after being severely punished by Lord Slug's immense power, Goku taps into a power that increases his power level to exceptional levels.
Though his hair doesn't change, he achieves what seems to be a golden aura, and his eyes are brimming with power. Fans have dubbed this form, False Super Saiyan, since he didn't fully turn into the golden warrior, but he did show clear signs of reaching that point.
12 Kaio-Ken
After reaching King Kai from running the long Snake Way bridge, Goku is taught how to increase his power level, speed, and strength, at the cost of his stamina. Fans first saw Goku use this red transformation in the iconic battle against Nappa and Vegeta.
After quickly disposing of Nappa, Goku pushes his Kaio-Ken transformation to times 20, showing the audience that he can multiply the Kaio-Ken power when necessary. This fight shows just how much Kaio-Ken can boost Goku's capabilities. The multiplication factor makes it a strong competitor against False Super Saiyan.
11 Super Saiyan 1
Arguably the most iconic transformation in all of Dragon Ball, is the Super Saiyan form. Goku first used this in his fight against Frieza, and the power boost that the form gave him allowed him to quickly overpower his sinister enemy. Fans of the show met the golden transformation with heavy appraise, and the look has been a stature of the show ever since.
In this fight, it was easy to say that this was Goku's strongest form at the time, and definitely one of the most memorable moments from the show.
10 Super Kaio-Ken
In the very first trial to combine Kaio-Ken with his Super Saiyan form, Goku created a brief appearance of what fans have called, Super Kaio-Ken. During Goku's fight with Pikkon, Goku surprised fans when he used Kaio-Ken while he was in his Super Saiyan transformation.
After doing so, he fought back against Pikkon with heavy offense, but unfortunately, he wasn't able to hold the form for very long, even in his dead body. This form is obviously more capable than his base Super Saiyan form, as he'd be multiplying the Super Saiyan's boost.
9 Super Saiyan 2
Most memorably associated with Goku's prodigy son, Gohan, is the famous Super Saiyan 2 form. Goku first reached Super Saiyan 2 after the Cell saga during his brutal fight with Majin Vegeta. This form was known by most fans as the form Gohan achieved when he fought against Cell.
It quickly became known as Super Saiyan 2, though Goku referred to it first as "Ascended Super Saiyan." This form was the second step that Goku took to achieve greater power, but shortly after, he showed fans he was capable of more.
8 Super Saiyan 3
After Goku showcased his Super Saiyan 2 form while fighting Vegeta, Goku yet again showed another transformation he achieved, all while fighting Majin Buu. Goku started to do the signature "scream-to-power-up," and he then turned into the intimidating Super Saiyan 3.
This form gave Goku incredibly long hair, and whenever he was in the form, he always seemed to have achieved a serious and clear mind. Though Buu didn't have much trouble fighting Goku in this state, it was clear that Super Saiyan 3 was a heavy force.
7 Golden Great Ape
One of GT Goku's newer forms is the Golden Great Ape. Fans who remember how Great Ape multiplied a Saiyan's power level, will know just how much strength Goku gained when he combined Super Saiyan and Great Ape together. From the show, it is even insinuated that the form is stronger than Super Saiyan 3, giving it a higher spot on this list.
In this form, it was clear that Goku did have trouble controlling the powerful form, but it gave him enough power to help in stopping Baby.
6 Super Saiyan 4
In Dragon Ball GT, Goku managed to control his Golden Great Ape form and fully transform into what would be known as Super Saiyan 4. This form might not be exactly more powerful than the Golden Great Ape form, but it definitely allows Goku to make his own decisions, be more agile, and more unpredictable.
This gives the Super Saiyan 4 form a definite advantage over its Golden Ape counterpart. This form was well-met in GT, standing to be one of the coolest looking forms, as well as the new title-holder of most powerful. (During its time, of course.)
5 Super Saiyan God
After GT was discarded from canon, the movie to follow the show years after would introduce a wild new transformation: Super Saiyan God. This form was only obtainable through the connection of five Saiyans, and it was said that the Saiyan who would become Super Saiyan God must be kindhearted.
After Goku achieved this form, he was visibly skinnier and had his base form style of hair, but it was glowing a bright red. He fought against the God of Destruction, Beerus in this form, and though he wasn't able to defeat Beerus, it showed how much more strength he gained from powering up.
4 Super Saiyan Blue
Immediately after obtaining Super Saiyan God, the form was quickly swept under the rug as Super Saiyan God Super Saiyan was introduced. The form was first used in a fight against Frieza, who had obtained his own form. This form practically is the combination of Super Saiyan, and god ki. Because of its long name, it was quickly referred to as "Super Saiyan Blue."
This form allows Goku to gain all the attributes from his newly acquired god energy, and multiply all of that power from his Super Saiyan abilities. This form became a staple for the new Dragon Ball Super show, and was Goku's strongest form for a while, until...
3 Super Saiyan Blue Kaio-Ken
Super Saiyan Blue was incredibly feasible on its own, but at some point Goku needed to go further than that. As fans saw way back in Goku's fight with Pikkon, Goku utilized Kaio-Ken to combine its power and multiplication abilities with Super Saiyan Blue.
This made Goku way stronger than he's ever been in the past, and he can even go further by simply multiplying his Kaio-Ken. Fans saw Goku use this while fighting the assassin Hit and showed just how capable the combination was.
2 Ultra-Instinct Omen
During Dragon Ball Super, one of Goku's most important moments from the show happened during the Tournament of Power. While fighting Jiren, Goku was struck by his own Spirit Bomb, and everyone assumed he would be out.
Goku, known for never giving up, was then shown to have absorbed some of the Spirit Bomb's energy and harnessed a power that made him involuntarily dodge, and attack faster than he has ever fought before. This Goku was entirely different from any of his other forms, because not only was it more powerful, but it wasn't a Saiyan form.
1 Mastered Ultra-Instinct
Finally, after having dealt with training to use Ultra-Instinct to its full potential, Goku was able to understand the power of Ultra-Instinct. Upon fully developing the ability to use Ultra-Instinct's power, Goku was able to achieve his Mastered Ultra-Instinct form. Visibly, it was different from his Omen form as it gave his hair a whiter appearance.
Combat-wise, it was a simple fact that he could fight much better, and allow his combat skills to kick in all while his body dodges attacks. This form is Goku's strongest form, and any opponent who forces Goku to this state will have much to deal with.
Dragon Ball Super is available to watch on Crunchyroll, Funimation, Hulu, and Amazon Prime.