Her father Cleomenes was the eldest-born son of the previous Agiad king, Anaxandridas II, and succeeded his father at his death; however, he had three paternal half-brothers, of whom the eldest, Dorieus, would cause him some trouble. The other two half-brothers were Leonidas I and Cleombrotus. All four were sons of Anaxandridas II, one of the dual kings of Sparta of the Agiad house.
According to one version (Herodotus's Histories, 5.4), Gorgo's grandfather Anaxandridas II was long married without children, and was advised to remarry (i.e. take a second wife) which he did. His second wife gave birth to the future Cleomenes I who was thus his eldest son; however, his first wife also became pregnant, and eventually had three sons, including Leonidas I. This version is however not supported by other sources, which imply that Cleomenes was either born by the king's first marriage or by a non-marital alliance. Most historians favor Herodotus because he is the earliest source. In either case, there appears to have been some tension between the eldest son and his half-brothers, resolved only by the former's death (or murder) and the accession of Leonidas I (at once his half-brother and his son-in-law).
According to Herodotus's Histories, at about the age of eight to nine years old, she advised her father Cleomenes not to trust Aristagoras of Miletus, a foreign diplomat trying to induce Cleomenes to support an Ionian revolt against Persians. "Father, you had better have this man go away, or the stranger will corrupt you". Cleomenes followed her advice.
Looking forward to Cleomenes' death, his only surviving child Gorgo became his sole heiress. She was apparently already married by 490 (in her early teens) to her half-uncle Leonidas I. Leonidas and Gorgo would have at least one child, a son, Pleistarchus, co-King of Sparta from 480 BC to his death in 459 BC/458 BC.
Arguably, Gorgo's most significant role occurred prior to the Persian invasion of 480 BC. According to Herodotus's Histories, Demaratus, then in exile at the Persian court, sent a warning to Sparta about Xerxes's pending invasion. In order to prevent the message from being intercepted by the Persians or their vassal states, the message was written on a wooden tablet and then covered with wax. "The Spartans", presumably the ephors, Gerousia or the kings, did not know what to do with the seemingly blank wax-tablet, until Queen Gorgo advised them to clear the wax off the tablet. She is described by David Kahn in his book The Codebreakers as one of the first female cryptanalysts whose name has been recorded.
According to Plutarch, before the Battle of Thermopylae, knowing that her husband's death in battle was inevitable, she asked him what to do. Leonidas replied "marry a good man who will treat you well, bear him children, and live a good life".
She had at least one son by Leonidas I, Pleistarchus, co-King of Sparta from 480 BC to his death in 458 BC.
Her son was a minor at his father's death, so his uncle Cleombrotus (died 480 BC) and then his first cousin and heir Pausanias (r. 480-479 BC) acted as his regent. It was Pausanias who was the architect of the combined Greek victory at the Battle of Plataea (479 BC). After Pausanias fell into disfavor and was accused of plotting treason, Leonidas's son Pleistarchus ruled with the other king of Sparta, Leotychidas II (and then his grandson Archidamus) until his death 459/458 BC.
There are sections where she is present at court or in council and gives advice to the king or the elders. This either indicates that Gorgo was highly thought of by Herodotus, who often left out the names of the female figures he included in his books, or that as the wife of Leonidas I, her actions and counsel were all the more noteworthy.
Plutarch quotes Queen Gorgo as follows: "When asked by a woman from Attica, 'Why are you Spartan women the only ones who can rule men?', she said: 'Because we are also the only ones who give birth to men.'" Another version has this as, "...some foreign lady, as it would seem, told her that the women of Lacedaemon were the only women in the world who could rule men; 'With good reason,' she said, 'for we are the only women who bring forth men.'" (Plutarch's Lives: Lycurgus)
Queen Gorgo was portrayed by Greek actress and future politician Anna Synodinou in the 1962 film The 300 Spartans.
Gorgo appears as a major character in Sacred Games, by Gary Corby.
The character makes a minor appearance in the 1998 comic series 300 by Frank Miller, who was heavily inspired by the aforementioned film. In the 2006 motion picture adaptation of the comic, 300, English actress Lena Headey plays Gorgo. In this version, she is given a more important role in the events surrounding the war with Persia; she tries to convince others to bring support to Leonidas, has sex with another council member to save her husband, and then kills that member and reveals him as a traitor. Headey reprised her role in the 2014 sequel, 300: Rise of an Empire.
Helena P. Schrader has published the first book in a three-part biographical novel on Leonidas and Gorgo. The first book, Leonidas of Sparta: A Boy of the Agoge, focuses on Leonidas boyhood in the infamous Spartan agoge, but books two and three will give prominence to Gorgo too.
Gorgo leads the Greek civilization in the strategic video game Civilization VI.