Echu mac Muiredaig (flourished mid 6th century) was a king of the Uí Cheinnselaig of South Leinster.
They belonged to a branch known as the Uí Felmeda descended from Fedelmid, son of Énnae Cennsalach, who was the father of Óengus.
An 11th-century poem Gein Branduib maic Echach ocus Aedáin maic Gabráin (The Birth of Brandub son of Eochu and of Aedán son of Gabrán) mentions that Echu was expelled from Leinster by his brother Fáelán and went to the court of Gabrán mac Domangairt, king of Dál Riata in Scotland.
The date of the poem coincides with a period of Scottish and Leinster cooperation and could be political propaganda.
Echu's son Brandub would go on to become King of Leinster and halt the expansion of the southern Ui Neill.