The Masraige were a Fir Bolg

Fir Bolg

In Irish mythology the Fir Bolg were one of the races that inhabited the island of Ireland prior to the arrival of the Tuatha Dé Danann.-Mythology:...

 tribe inhabiting Magh Slécht

Magh Slécht

Magh Slécht is the name of an historic plain in Ireland. It comprises an area of about three square miles situated in the south-eastern part of the Parish of Templeport, Barony of Tullyhaw and County of Cavan. It is bounded on the north by Templeport Lough, on the east by Slieve Rushen mountain,...

  in County Cavan

County Cavan

County Cavan is a county in Ireland. It is part of the Border Region and is also located in the province of Ulster. It is named after the town of Cavan. Cavan County Council is the local authority for the county...

, Ireland. They were also called Masragii, Masraide, Masraidhe, Masruidhe, Mascraide, Masree or Mascraidhe. The name can be translated as "Lords of Death" or "Beautiful Lords".

History

The Lecan Genealogies in Corpus Genealogiarum Hiberniae 1 16r A44, 279, states that the Masraige are descended from Fergus Mac Roich

Fergus mac Róich

Fergus mac Róich is a character of the Ulster Cycle of Irish mythology...

 of the Red Branch

Red Branch

The Red Branch is the name of two of the three royal houses of the king of Ulster, Conchobar mac Nessa, at his capital Emain Macha , in the Ulster Cycle of Irish mythology...

 Knights of Ulster. The Cíarraige

Cíarraige

The Ciarraige were a population-group recorded in the early historic era in Ireland.The Ciarraige were a people found scattered over much of Ireland...

 also claim the same descent.

Masraige is mentioned in Life of Dallán Forgaill

Dallan Forgaill

Saint Dallán Forgaill —also Dallán Forchella; Dallán of Cluain Dalláin; born Eochaid Forchella—was an early Christian Irish poet best known as the writer of the Amra Choluim Chille and the early Irish poem Rop tú mo baile, the basis of the modern English hymn Be Thou My Vision.-Personal...

as his birthplace.

Also in the Annals of the Four Masters, they are mentioned as having killed Conall Gulban

Conall Gulban

Conall Gulban was an Irish king who founded the kingdom of Tír Conaill in the 5th century, comprising much of what is now County Donegal. He was the son of Niall Noígiallach....

 -"M464.3 Conall Gulban, son of Niall of the Nine Hostages (from whom are descended the Cinel Conaill), was slain by the old tribes of Magh Slecht, he having been found unprotected, and was buried at Fidhnach Maighe Rein, by Saint Caillin, as the Life of the aforesaid saint relates."

The Book of Fenagh mentions them as follows-

Page 89

“I prophesy thee, without anguish.
Give me my tribute every time,
as Conall Gulban gave it.
Conall was the first king of Tara,
of the Clann-Neill, without dispute.
'Till he was slain in prosperous Magh-Rein,
sixteen years he happily spent.
The Masraighe went to the East
once, on a great foray to Tara;
Whereupon Conall quickly came,
to Magh-Rein, in pursuit of them.
A flying spear killed the king,
on that journey, without falsehood,
on Magh-Rein, at Dun-baile,
of which the Masraighe boasted.
Conall was interred in the earth,
between the Lake and the Dun.”

Page 139

“One time the Masraidhe of Magh-Slecht went on a predatory expedition
to Tara, when they brought a prey of horses with them from the east.
Conall, on hearing the shoutings, proceeded with the small number that was
near him at the time; and he ceased not from [pursuing] them until he came
to Dun-Conaing on Magh-Rein, to wit, Fidhnacha at this day. And the old
Tuatha-Slecht slew him, because he was unarmed; and that would not have
been an occasion of slaughter to them, if luck had not willed. Or it is a
flying spear that killed him. But whichever of them was his [manner of]
death, it was the Masraidhe that committed the deed. Howsoever, the stone
and grave of Conall were placed on Magh-Rein, at Dun-Baile.”

Page 145

“Dun-Conaing was this place [called], till to day,
during the time of sixty prosperous kings,
until Conall son of Niall fell,
by the sons of the Liath, over the gap of treachery.
Berna-in-braith was its name until this day,
from the betrayal of Conall, the head of the host;
Fidhnacha of Caillin son of Niata
shall be its name, without falsehood, to the day of doom.
In pursuit of horses he stoutly came,
from the east, from Tara of the flocks,
with a small company; 'twas a foolish journey,
for he was slain by the old Tuatha-Slecht.
Being without a shield against lance-thrusts
was what caused the king his mortal wound.
Too many men, and too many weapons,
found the man at a disadvantage.”

The Masraige were one of the Aithechthúatha, a generic designation for certain Irish ethnic groups, usually translated as "rent-paying tribes", "vassal communities" or "tributary peoples". The term meant any tribe which did not belong to the ruling dynasties (such as Uí Néill

Uí Néill

The Uí Néill are Irish and Scottish dynasties who claim descent from Niall Noigiallach , an historical King of Tara who died about 405....

 or Eóganachta

Eóganachta

The Eóganachta or Eoghanachta were an Irish dynasty centred around Cashel which dominated southern Ireland from the 6/7th to the 10th centuries, and following that, in a restricted form, the Kingdom of Desmond, and its offshoot Carbery, well into the 16th century...

) who were overlords of the older tribes. The Masraige were conquered by the Uí Briúin Bréifne in the 6th century.