An alien race of physically powerful savage beings.
The Saiyans were a group of barbaric aliens who came to the Tuffles' cities to take their territory and technology however their original home world was destroyed by the first Super Saiyan, the Original Super Saiyan. When the Saiyans first arrived they met the friendly Tuffles, an advanced scientific race who had no way of knowing the Saiyans would eventually take the whole planet for themselves and destroy their race. One day a civil war broke out and the Saiyans tried many times to overthrow the Tuffles but were unsuccessful, although the Saiyans were bigger in size and much stronger, they were fewer in number compared to the Tuffles. What also gave the Tuffles a upper hand was that they had technology to read the power levels of the Saiyans and advanced weaponry to hold them off. Then one night the Saiyans were able to transform into Great Apes ( Oozaru) thanks to the full moon that only came once every 100 years, with this they finally annihilated the Tuffles and had the planet renamed into Planet Vegeta its former name being Planet Plant. After their victory the Saiyans built a rocket ship and traveled to a near by planet called Arcose were they meet the Arcosians (little is know about this race as they are only mentioned once in the series by King Kai), now the Arcosians had money and technology but the planet Arcose was a dump, so they hired a group of Saiyans to take over a planet for them and in return they would share their technology with them. Over the years the Saiyans also learned how to use the Tuffles' advanced equipment and become smarter and less barbaric, although they still lusted for fighting and destruction. At some unknown time following the Saiyan victory the planet was conquered or annexed by Frieza's empire and the Saiyans (like many other races) were drafted to serve as soldiers in Frieza's military under the World Trade Organization. Because of the Saiyans' innate strength and penchant for violence, they were considered to be useful mercenaries and assisted in the conquering of many planets, or if assignment called for, eradication of the planet's population. (Even Saiyan children were considered powerful enough to conquer some of the weaker planets, such as Earth.) Eventually, seeing how quickly some of the more gifted Saiyan warriors were gaining power through battle, Frieza grew concerned with the potential of the Saiyan race and thought that they would grow strong enough to face him or even become the fabled Super Saiyans, able to defeat him in battle so the maniacal warlord destroyed Planet Vegeta, almost eradicating the Saiyan race. Only four pure-blood Saiyans survived the destruction, Kakarot ( Goku), Vegeta, Nappa and Raditz as they were not on the planet at the time. Once the latter three discovered that their planet's destruction, Frieza lied to them that an asteroid had hit their world, and offered them continued employment in return for eventual wealth.The Saiyans were avenged when Son Goku defeated Frieza on Namek. Frieza later met his end on Earth when Future Trunks killed him. In the anime only, four more Saiyans survived the catastrophe, appearing in the Dragon Ball Z movies. Turles, Broly, Paragus, and Tarble. As a side note, a common racial slur towards Saiyans is the term "monkey" or "ape".
Saiyans are very outwardly similar to humans the only exception being the Saiyans' monkey-like tails. They are commonly known to have deep black hair however in some rare occasions some Saiyans are seen to have dark brown hair (Vegeta's hair is arguably dark brown) or even brown hair (King Vegeta). Vegeta has stated that the hair of a pure-blooded Saiyan does not change since birth however this is contradicted by the fact that when Vegeta was a child he had strands of hair hanging in front of his forehead but later this changes and he gains a widow's peak, perhaps he cut his hair however this is highly unlikely, its more likely this was a mistake by the animators of the show. This however is not the case with half Saiyans such as Gohan, Goten and Trunks who had been shown to have different lengths of hair and have different hair styles, just like humans. Another issue is Nappa who used to have hair in the past as shown in Bardock: The Father of Goku however he seems to have lost it as the years past. Saiyans also have dark eyes however half-breed Saiyans don't always, Vegeta's children Trunks and Bra both have inherited blue irises from Bulma.
These similar appearances can be noted in:
All pure-blooded Saiyans and some half-breeds are born with tails, monkey-like in appearance and the tail is also covered with brown fur. The tail is an extremely sensitive and vulnerable area when grabbed or injured, it causes immense pain to the owner and temporarily immobilizes the entire body. However Saiyan elite warriors can train themselves to overcome this natural weakness as did Vegeta, Nappa and also Goku (who was not elite at the time he did this nor was he aware of being an alien) and the tail becomes no more fragile than any other limb. The tail can be used to grasp or grab things like other primates, it has been mentioned that a Saiyan with a tail gains more power than a Saiyan without a tail. The tail also allows the Saiyan to transform into giant ape-like creatures called Great Apes and potentially a Super Great Ape or a Golden Oozaru however if the tail is removed the power is lost. Some Saiyans have the ability to regrow their tails however at a certain period of time the Saiyans eventually loses this regenerative ability, Gohan for example who is not even a pure-blooded Saiyan has had his tail removed and has regrown it multiple times until it is cut off by Vegeta. Vegeta had his tail cut off in battle however he is an adult and it is noted that it never grew back however in Dragonball GT it grows back but through artificial means.
Saiyans have two types of transformations, the Great Ape transformation (the ability to transform into a giant ape under a full moon) granted to them by their tails, and the Super Saiyan transformations of legend. While certain conditions must be met for the transformations to take place, it has been proven that any Saiyan (or even human-saiyan hybrid) can achieve these transformations, with the exception of the Legendary Super Saiyan form (unique to Broly) and Super Saiyan 4 (only achievable by pure-blood Saiyans). Each of these transformations can be read about in much more detail on their respective pages.
Saiyans even at birth have a war-like personality having a passion for fighting, conflict and destruction and they choose violence over peace with others. Saiyans are typically more barbaric than humans and are aggressive, hard-headed and have short explosive tempers. They are an intensely proud people with great honor social hierarchy and they take great pride in their fighting ability being often arrogant and haughty, they also let their emotions get the better of them when aroused in stimulating situations which results in them making rash decisions. Saiyans also appear to lack sympathetic emotions as though by choice rather than nature as shown by their lack of fear and death and uncaring towards siblings and example is Raditz brutally beating his long-lost brother Goku and Vegeta's lack of care and concern for his father's death. A possible reason could be that their society was corrupted in that area as a result of being occupied by Frieza however this is debatable as even before Frieza discovered the Saiyans they seemed to be barbaric and sadistic. Both Vegeta and Nappa have both shown no sympathy towards their fallen comrade Raditz and merely laughed and called him a "weakling" although Nappa did suggest bringing Raditz back to life by using the Dragon Balls. Vegeta and Nappa have displayed to have had a good friendship during the past however Vegeta however Vegeta was not reluctant to kill Nappa and he did not hesitate to do so after Nappa displayed cowardice and weakness by panicking at Goku's power. Most Saiyans also possess keen fighting sense and great fighting ability which allows them to learn new fighting styles, achieving new transformations and learning to detect and sense ki. Bardock is stated not to have been evil as he ws shocked and saddened at seeing his crew and his best friend Tora slaughtered by Dodoria. Bardock implied to not being evil as when he was facing Frieza his words were "This is for all the people we killed in your name" implying that he is not evil and it may also be implying that he was saying this as a sign of regret for committing numerous murders for Frieza, one of Bardock's final words were that he wished he could hold his son Goku in his arms, Bardock is quite possibly the first Saiyan to show true emotion however Vegeta has shown to express emotion such as when Future Trunks was killed by Super Perfect Cell and when Frieza killed him. Broly in particular seems to have a personality that no Saiyan has displayed, Broly is possibly the most destructive and violent Saiyan to ever be known as he is not simply thrilled by battle but is uplifted by the very thought of destruction, he has demonstrated his lust for destruction such as when he destroyed the home planet of alien slaves simply to watch them suffer, he has shown no sympathy or emotion towards his father Paragus as he gouged out his father's left eye without regretting his actions, Broly has also demonstrated surges of uncontrollable rage and his personality is similar to a psychopath or it is quite possible that he is psychopath himself and is mentally insane, he is also shown to be unbelievably sadistic as he prefers to make his victims suffer than kill them and his fighting style is specifically designed for causing pain such dislocating body parts, clotheslines and crushing his opponents body by continuously jumping on them causing them to gush blood, Broly also uses sadistic sarcasm such as "If you'd just let me kill you before you wouldn't be dealing with this pain now" and when Gohan demanded that he stop his rampage Broly responded by saying "Not until you lie dead at my feet", he also mocks his feeble opponents throughout his slaughter, Broly is quite possibly the only Saiyan to ever display this sort of psychotic personality and insanity, it has been speculated that Broly's uncontrollable personality is due to the fact that Broly was born next to Goku and during their time as babies Goku's unbearable crying did not allow Broly to have proper mental development however this cannot be the reason for his love of destroying everything in existence as it is highly unlikely. Paragus is also one of the Saiyans who has shown signs of sympathy and regret such as when he pleaded King Vegeta not to execute Broly(Broly was an infant at the time) and he displayed signs of regret for attempting to leave Broly on a planet in the way of an approaching comet.
Saiyans have an inborn need to fight. Most Saiyans will spend their lives training to become stronger so that they can prove themselves in battle. When Frieza hired the Saiyans as his planet brokers, he knew of their amazing fighting skills and used that to his advantage. However, Frieza began to notice how powerful the Saiyans were becoming and began to fear that one day one of them would overwhelm him as the most powerful being in the universe. This eventually lead to Frieza's destruction of Planet Vegeta and all the Saiyans on it. Saiyans like Goku and Vegeta are frequently seen training and improving their fighting skills to keep up with each other's skills and the appearance of new, more powerful foes.
Many of the Saiyan/Human hybrids that appear throughout the series possess extreme fighting potential. It is also very common for them to develop the ability to transform into Super Saiyans at childhood, thought to be particularly likely when the hybrid's Saiyan parent had achieved the transformation prior to conception.
In Dragon Ball GT, Saiyan hybrids seem to have less potential than full-blooded ones, and female hybrids appear to be weaker. Of particular note is Pan, who fails to achieve even the first Super Saiyan transformation, though her grandson Goku Jr. still had enough Saiyan blood to wield it.
Saiyan Armors are standard armor of Saiyan Warriors and later standard issue for Frieza's army. They're made of an unknown material, which is said to be stretchy yet hard (Gohan once remarked "one size fits all"). Even Gohan is able to wear armor that was meant for adults without having any size issues. However, they are known to shatter when dealt enough damage, showing that they are indeed hard and solid. The most commonly seen ones have dual shoulder guards and some form of skirt armor or crotch guard. Matching boots (often white in color, but others do exist) are standard issue, as is a pair of white gloves or fingerless wrist guards. Standard armor has large shoulder plates, but some simply have reinforced shoulder straps. Many also have skirt armor or plate shielding the groin. Most Saiyans wrap their tails around the armor's waist, appearing as if they have a furry belt. Saiyan armor for woman do exist too, but this is only seen in the Bardock special as Fasha and some woman in a bar are wearing it, and none is seen in the manga. It does not include the crotch guards or the shoulder plates, and looks like Vegeta's jumpsuit, but having one strap, same body armor, knee pads with a covering on one leg, and white gloves and boots.
We see Vegeta wear this when he is traveling to Earth in the Saiyan Saga. When he actually arrives on Earth the armor is much more like the armor Nappa is wearing in the next image. The only thing that sets it apart from regular Saiyan armor is it's coloring. It should be noted though that this only occurs in the anime as, at the time the scene was animated, no official colored scenes of Vegeta or Nappa had been introduced in the manga so TOEI had to make up their own color schemes.
This is a variation on the above armor that Bulma makes for Goku, Gohan, Vegeta and Future Trunks. They all wear a blue jumpsuit under the armor that covers the whole back from the neck down. The armor is again white with a yellow section, but only covers the chest. The shoulder guards are now nothing but two little straps made of the same yellow material. White gloves and yellow tipped boots are also worn with the outfit. We mostly see this armor worn in the Hyperbolic Time Chamber and considering the time this outfit was worn and how much training was done in them they held up well. When Vegeta wears the armor he decides to keep his blue jumpsuit, white gloves, and boots as his standard battle outfit but loses the chest piece, possibly due to weight issues.
Armor in this style is also worn by members of Bardock's team, despite its being invented long after their deaths. Note that Since Bardock and his crew were low-class warriors, they might have modified their armor in the field to suit their needs, unintentionally recreating the look of the newer models.
Paragus wore a unique Saiyan armor during his appearance in Movie 8. Its overall design resembled the clothing of those on Yardrat. His gloves and boots were purple throughout most of Movie 8, though in a few flashbacks his gloves, boots, and armor were differently colored (I.E yellow/orange).
In addition to the name "Saiyan" being an anagram of the Japanese word for vegetable, most pure-blooded Saiyans in the series also have names with vegetables puns-- either in English or Japanese. Furthermore, the Saiyan Royals are keeping in line with this, simply named Vegeta(ble).