Medb was the favoured daughter of Eochaid Feidlach, the High King of Ireland. Medb came to power as Queen of Connacht through her arranged marriage to Conchobar mac Nessa, King of Ulster. Medb bore him a son, named Glaisne but their marriage was an unhappy one, and so she soon left him. Conchobar remarried another of Eochaid Feidlach’s daughters, Eithne, and she soon fell pregnant to him. Medb had her killed, and her son, named Furbaide, was cut from her posthumously.
Medb’s father deposed the King of Connacht, Tinni mc Conri, and replaced him with Medb as sole ruler. Medb took Tinni as a lover, and through his relations with her he regained some power within Connacht, though she would not marry him and remake him King.
At a meeting in Tara, Conchobar raped Medb, and as a result the High King waged war against Ulster. Tinni, because of his love for Medb, challenged Conchobar to single combat but was killed. The Connacht army retreated, protected by Eochaid Dála of the Fir Domnann tribe. Medb took him as a lover, and later husband, making him King of Connacht. While married to Eochaid Dála, Medb took her chief bodyguard, Ailill mac Máta as a lover, and upon finding out about the affair Eochaid Dála challenged him to single combat and lost. Medb married Ailill, and they ruled together as King and Queen of Connacht, having seven sons and one daughter.
Medb long insisted that she be of equal wealth to Ailill. Upon finding out he was one prize bull richer than her, she searched Ireland for one which would match it, eventually finding one in the possession of Dáire mac Fiachna, a vassal of Conchobar. She offered weath, sex, and land in return for the bull and Dáire accepted, though her drunken messenger admitted that had he not accepted, Medb would have taken the bull by force. Dáire rescinded his offer, and Medb, astounded at his insolence and unused to refusal, prepared for war. Her army was made of contingents from all over Ireland: amongst their leaders was Conchobar’s estranged son Cormac Cond Longas, and her favoured lover, Fergus mac Róich. Medb’s army was defeated by Cúchulainn due to a curse placed on the Ulstermen who fought for her, but she managed to retrieve the bull before beating a hasty retreat. She pitted her bull against Ailill’s, and it won, though later died of its wounds.
Medb is one of Ireland’s most enigmatic and famous legendary figures, a Queen in her own right and a powerful, ruthless ruler. She was sexually voracious, taking multiple lovers - one poem about her claims it took sex with seven men to satisfy her, though Fergus was able to satisfy her after only one visit. Medb is accredited with seducing Fergus away from his duties to Ulster, as he famously “preferred the buttocks of a woman to his own people.” She demanded three qualities of her husbands after Conchobar: to be without fear, without meanness, and without jealousy. Medb lived into her old age, and was eventually killed by Furbaide, her nephew, in revenge for his mother. She was known to bathe in a pool in Inis Cloithreann, and so Furbaide went there every day and practiced with his sling until he could hit an apple on the top of a pike which was the same height as Medb. He killed her there, while she bathed. Her seat was what is now Rathcrogan in Roscommon, and she is said to be buried in a 40-foot-tall cairn in Cnoc na Ré, Sligo. She had a vitriolic hatred for the men of Ulster, and is said to be buried upright, facing them down even in death.