Medb, later spelled Meadhbh, Méabh(a) and Méibh, and often anglicised as Maeve, is queen of Connacht in the Ulster Cycle of Irish mythology. Her husband in the core stories of the cycle is Ailill mac Máta, although she had several husbands before him who were also kings of Connacht. She rules from Cruachan. She is the enemy of Conchobar mac Nessa, king of Ulster, and is best known for starting the Táin Bó Cúailnge to steal Ulster's prize stud bull Donn Cúailnge.

The Ulster Cycle, formerly known as the Red Branch Cycle, is a body of medieval Irish heroic legends and sagas of the Ulaid. It is set far in the past, in what is now eastern Ulster and northern Leinster, particularly counties Armagh, Down and Louth. It focuses on the mythical Ulster king Conchobar mac Nessa and his court at Emain Macha, the hero Cú Chulainn, and their conflict with the Connachta and queen Medb. The longest and most important tale is the epic Táin Bó Cúailnge. The Ulster Cycle is one of the four 'cycles' of Irish mythology and legend, along with the Mythological Cycle, the Fianna Cycle and the Kings' Cycle.