Máel Bressail mac Ailello (died 825) was a king of Ulaid, which is now Ulster, Ireland.
He belonged to a branch of the Dal nAraide known as the Uí Echach Cobo in the west part of county Down.
He was the first member of the Uí Echach Cobo to hold the throne of all Ulaid since Fergus mac Áedáin (died 692) who was his great-great grandfather.
His exact year of accession to the throne of Coba is unknown though his brother is the last king mentioned in the Annals of Ulster prior to him.
In 819 Máel Bressail was able to acquire the throne of Ulaid after internal squabbling among the Dal Fiatach.