Conaing mac Flainn (died 849) was a King of Brega from the Uí Chonaing sept of Cnogba (Knowth) of the Síl nÁedo Sláine branch of the southern Ui Neill.
He was the son of Flann mac Congalaig (died 812), a previous king.
The Uí Chonaing sept had conquered the lands of the Ciannachta (south of the Lower Boyne in modern County Meath) and were normally styled Kings of Ciannachta in this period.
In 841 Conaing had a rival from his own kin Áed, son of Dúnchad, killed by his associates in his presence.
His daughter Gormlaith ingen Conaing mac Flainn was the wife of Flann Sinna (died 916).