LEINSTERLEINSTER
Leinster, or
Cóiced Laigen
(the Fifth of the Laigin), is
one of the ancient provinces of Ireland. The dominant
inhabitants were the Laigin, who believed they came
from Gaul in prehistoric times. There were links across
the Irish Sea in the early centuries
C
.
E
., for the Lleyn
peninsula in Wales takes its name from the Laigin.
Traditions preserved in historical tales and the annals
show that the Laigin controlled a vast territory before
the sixth century, including much of Brega and Mide;
this land was ultimately lost to the Uí Néill, but there
were Laigin kings of Tara before the reign of Niall
Noígiallach. By the seventh century, Leinster’s bound-
aries extended from the valley of the Liffey westwards
to the Slieve Bloom Mountains, then southward around
the highlands of Osraige and down the Barrow val-
ley to the sea. It was divided into north Leinster,
Laigin
Tuathgabair
, and south Leinster,
Laigin Desgabair
,
and kings in each area enjoyed a considerable degree
of independence. The main settlement was in the val-
leys of the Liffey, Barrow, and Slaney, and in the plains
of Wexford and Kildare. In the latter area is the hillfort
of Dún Ailinne (Knockaulin), a site comparable to Tara
or Emain Macha, and an important centre of the early
Leinster kingship.
From the seventh century to the twelfth, the lead-
ing dynasties were Uí Dúnlainge in the north and
Uí Chennselaig in the south, but other Laigin groups had
been paramount in Leinster beforehand. Uí Garrchon
were settled in the Liffey valley, and at least two of
their kings of Leinster fought against the Uí Neill
around the end of the fifth century. Uí Enechglaiss also
provided early provincial kings. These dynasties suf-
fered as a result of Uí Neill expansion and were ousted
from their fertile lands by Uí Dúnlainge, resettling east
of the Wicklow Mountains. Uí Dúnlainge then strove
for power with the Uí Máil. A few Uí Máil dynasts
succeeded to the provincial kingship, the last being
Cellach Cualann (d. 715). Subsequently, Uí Máil
were deprived of both the Leinster kingship and the
fertile lowlands by Uí Dúnlainge. Also significant were
Uí Failge, who occupied the boggy lands at the head-
waters of the Barrow. They had previously ruled a
larger territory, but also suffered from Uí Néill
encroachments. The Loígis were settled southeast of
Slieve Bloom and were totally unrelated to the Laigin.
They had the status of favored vassals of the Leinster
kings, principally for their role as defenders of this
border area. A further non-Laigin people were the
Fothairt, who were scattered throughout Leinster, and
to whom St. Brigit belonged.
In south Leinster Uí Chennselaig were dominant by
the eighth century, but here too were earlier Laigin
dynasties. Uí Bairrche occupied lands in Carlow, but
were divided by Uí Chennselaig expansion so that one
branch remained in the middle reaches of the Barrow
valley, and another moved southwards to the Wexford
coast. Also in south Leinster were groups of Fothairt,
associated with Uí Bairrche, and a people called the
Benntraige.
After 738, Uí Dúnlainge excluded all other peoples
from the Leinster kingship. Their ascendancy was
gradually eroded by the Uí Néill, who regularly tried
to gain the submission of Leinster’s kings. The dep-
redations of Viking incursions also had a destabilizing
effect on the Uí Dúnlainge hegemony; its decline was
accelerated by the interference of the kings of Munster
and Osraige. The establishment of the Viking settle-
ment at Dublin in 841 was of undoubted significance,
creating new maritime links, and providing a center
of wealth on Leinster’s doorstep. By the eleventh
century, Dublin and its hinterland, Fine Gall, were
closely linked to Leinster, and Irish kings strove for
dominance over the rulers of the city and control of
its resources. Meanwhile, Leinster had become a sig-
nificant factor in the struggle for high kingship
between Uí Néill and the Dál Cais. Domination by
their kings and the kings of Osraige fatally under-
mined Uí Dúnlainge authority, and in 1042 Diarmait
mac Máele-na-mBó of Uí Chennselaig took the Leinster
kingship. Though ultimately unsuccessful in his chal-
lenge for the high kingship, he achieved more than
any previous king of Leinster. Control of Dublin had
been a key factor in his success, and this lesson was
not lost on his contemporaries. His descendants, the
Meic Murchada (Mac Murroughs) retained the pro-
vincial kingship and played an important role in later
interprovincial struggles. A pivotal role was played
by Diarmait Mac Murchada, whose expulsion from
and return to Ireland led to the Anglo-Norman Invasion.
Subsequently, a considerable number of colonists
entered Leinster, notably the de Clares and Fitzger-
alds, and established lordships in Kildare, Carlow,
and Wexford.
The Mac Murroughs retained a degree of power in
south Leinster, though hemmed in by the English. This
changed with the career of Art Mór Mac Murchada
Caomhánach from the 1370s to 1416, who created a
solid kingdom in Carlow and northern Wexford, and
Mac Murroughs succeeded to the title “king of Leinster”
down to the sixteenth century. Uí Dúnlainge, repre-
sented principally by the families of Ua Broin
(O’Byrne) and Ua Tuathail (O’Toole) were driven by
the invaders from their lands into the Wicklow Moun-
tains, thus suffering the fate they had inflicted on
Uí Garrchon and Uí Máil centuries earlier. However,
both families were able to create enduring Gaelic
lordships in the highland fastnesses. The O’Tooles
were often enemies of the English crown, but ulti-
mately in 1541 Tairrdelbach Ua Tuathail submitted