Maine of Tethba or Maine mac Néill was a supposed son of Niall Noigiallach. His existence is very doubtful. Writing of him in 1973, Irish historian Francis John Byrne

Francis John Byrne

Francis John Byrne is an Irish historian.Born in Shanghai where his father, a Dundalk man, captained a ship on the Yellow River, Byrne was evacuated with his mother to Australia on the outbreak of World War II...

 stated his belief that:

We may suspect then that eastern Maine was so successfully absorbed into the Uí Néill ambit that their kings, by a polite fiction, were accepted into the dominant dynasty circle ... The fact that the annalistic obit of Maine mac Néill in 440 is so much earlier than that of any of his supposed brothers also suggests that he was adopted into the dynasty some time after the synthetic historians had agreed to push back the date of Niall's reign by a generation or more. [Byrne 1973:92–93]

It is actually far more likely that Maine was the ancestor of the Uí Maine, whose kingdom once covered a region over the entire of what is now County Galway

County Galway

County Galway is a county in Ireland. It is located in the West Region and is also part of the province of Connacht. It is named after the city of Galway. Galway County Council is the local authority for the county. There are several strongly Irish-speaking areas in the west of the county...

 north and east of Athenry

Athenry

Athenry is a town in County Galway, Ireland. It lies east of Galway city, and one of the attractions of the town is its medieval castle. The town is also well-known by virtue of the song "The Fields of Athenry".-History:...

, all of south County Roscommon

County Roscommon

County Roscommon is a county in Ireland. It is located in the West Region and is also part of the province of Connacht. It is named after the town of Roscommon. Roscommon County Council is the local authority for the county...

, and stretching over the River Shannon

River Shannon

The River Shannon is the longest river in Ireland at . It divides the west of Ireland from the east and south . County Clare, being west of the Shannon but part of the province of Munster, is the major exception...

 into the regions called Cenél Maine, Cuircni, Calraige and Delbhna

Delbhna

The Delbna or Delbhna were an ethnic group in Ireland. They had a number of branches in central and western Ireland.*The Delbhna Tir Dha Locha were the most westerly branch, based in Iar Connacht....

 Bethra. Cenél Maine lay in the south-west portion of the kingdom of Tethbae

Tethbae

Tethbae, also Tethba and other variants, and often anglicized Teffia, was a region of Ireland in the Middle Ages. It was divided into two distinct kingdoms, north Tethba, ruled by the Cenél Coirpri, and south Tethba, ruled by the Cenél Maini...

 – on the east shore of Lough Ree

Lough Ree

Lough Ree is a lake in the midlands of Ireland, the second of the three major lakes on the River Shannon. Lough Ree is the second largest lake on the Shannon after Lough Derg. The other two major lakes are Lough Allen to the north, and Lough Derg to the south, there are also several minor lakes...

 – and when it was taken over by the 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....

, its ruler's ancestor was given a pedigree making him a son of Niall.

Ui Many remained a powerful independent kingdom in its own right for several further centuries.