Amalgaid mac Fiachrae (Old Irish: Amalgaid mac Fiachrach Ogham script: ᚐᚋᚐᚂᚌᚐᚔᚇ ᚋᚐᚉ ᚃᚔᚐᚉᚆᚏᚐᚓ) (died 440)[1] was a King of Connacht of the Ui Fiachrach sept.
He was the son of Fiachrae mac Echach Mugmedóin and grandson of the high king Eochaid Mugmedón (died 362).
[2] He is mentioned as king of Connacht in the Laud Synchronisms and the Book of Leinster which gives him a reign of 34 years.
A succession dispute broke out upon his death in Tír Amhlaidh between his sons Óengus and Éndae.
Endae had his son Conall baptised and given to Patrick's service for his support.