The Amazons were the epitome of "grrrls" - mean archers, skilled swordfighters, and born to ride on horseback. And they might have been real.
Let's begin with the legends surrounding the Amazons. In Greek mythology, Amazons are seen as equals of Greek warriors; sometimes the Greeks are shown subduing them, but often the two sides are shown fighting bitterly but with no clear winner. Achilles, a hero of the Trojan War, fatally wounded Penthesilea, the queen of the Amazons in battle; when he removed her helmet, he found the beautiful but dying woman beneath. Of course, he felt guilty, and the surrounding Greek warriors wished their wives could be like her.
And now for the evidence: Greek Amazons might have been specifically based on a nomadic tribe called the Scythians or Saka-Scythians, who lived in what is now Kazakhstan. Scythian women didn't dominate their society, but they certainly were equals of the men, especially when it came to fighting. Several Scythian warrior graves have been found, and although many of the skeletons were dismissed as male after armor and weapons were uncovered in the tombs, some of them have since been re-identified as young women!
Also, as Stanford researcher Adrienne Mayor notes in her book, The Amazons, the single most well-known "fact" about Amazons, the one about boob removal, is entirely false. The misconception probably came from several sources: one inexperienced etymologist decided that the word "Amazon" came from the Greek for "without breasts." (It doesn't; "Amazon" is likely a foreign loanword.) Also, the inspirations for the Amazons - real-life Central Asian nomad women - wore flat chest armor, as pictured above. But why? Well, the sexy fantasy battle bras you might see in video games and art would actually increase the risk of death by heart-piercing. A sword would be deflected by shaped breast armor, but it would be deflected toward that sharp little piece of metal over a warrior's heart. Thus the reason for the armor that produced the urban myth.