Síl nÁedo Sláine (Old Irish: [sʲiːlʲ ˈnaiðo ˈslaːnʲe]) are the descendants of Áed Sláine (Áed mac Diarmato), son of Diarmait mac Cerbaill.
Part of the Southern Uí Néill—they were the kings of Brega—they claimed descent from Niall Noígiallach and his son Conall Cremthainne.
The other main branch was that of Áed's son Diarmait, which ruled southern Brega from its seat at Loch Gabhair.
From Blathmac, whose sons Sechnassach and Cenn Fáelad were both High Kings, descended the Uí Chinn Fháelad.
The Síl nDlúthaig took its name from a son of Ailill Cruitire, Dlúthach, but this was another minor group.