Selaig:  Sheelagh, a townland in the barony of Upper Dundalk

Semne:  Island Magee, north-east of Carrickfergus, in the County Antrim

Senbothae:  Templeshanbo, at the foot of Mount Leinster, in the County
Wexford

Sencha macAilella:  the wise counsellor and judge of the Ulstermen

Sered:  a plain in the north of the barony of Tirhugh, County Donegal

Setanta:  the real name of Cuchulain

Sid:  the terrene gods (pronounced She)

Sil:  in Lecale, in the County Down

Sinann:  the river Shannon

Siuir:  the Suir, a river in Munster, forming the northern boundary of the
County Waterford

Slabra:  a place north of Selaig, near Kells, in Meath

Slaiss:  south-east of Cruachan, between Ord and Inneoin

Slane:  a town on the Boyne, in Meath

Slechta:  south-west of Kells, in Meath

Slemain Mide:  “Slane of Meath,” Slewen, three miles to the west of
Mullingar, in Westmeath

Sliab Betha:  Slieve Beagh, a mountain whereon the Counties of Fermanagh,
Tyrone, and Monaghan meet

Sliab Culinn:  Slieve Gullion, in the County Armagh

Sliab Fuait:  the Fews Mountains, near Newtown-Hamilton, to the west and north-west of Slieve Gullion; in the southern part of the County Armagh

Sliab Mis:  Slieve Mish, a mountain in the County Kerry, extending eastwards from Tralee

Sliab Moduirn:  the Mourne Range, in the County Monaghan, partly in Cavan and partly in Meath

Sruthair Finnlethe:  a river west of Athlone

Sualtaim (or, Sualtach) Sidech:  the human father of Cuchulain

Suide Lagen:  Mount Leinster, in the County Wexford

Tadg:  a river in Conalle Murthemni

Taidle:  near Cuib

Taltiu:  Teltown, in the County Meath, on or near the Blackwater, between
Navan and Kells; one of the chief places of assembly and burial of the
Ulstermen

Taul Tairb:  in Cualnge

Telamet:  a river in Conalle Murthemni

Temair:  Tara, the seat of the High King of Ireland, near Navan, in the
County Meath (pronounced Tavvir)

Tethba descirt:  South Teffia, a territory about and south of the river
Inny, in the County Longford

Tethba tuascirt:  south-east of Cruachan, in Teffia, County Longford

Tir Mor:  in Murthemne

Tir na Sorcha:  a fabled land, ruled over by Manannan

Tir Tairngire:  “the Land of Promise”

Tonn Clidna:  a loud surge in the Bay of Glandore

Tonn Rudraige:  a huge wave in the Bay of Dundrum, in the County Cork

Tonn Tuage Inbir:  “the Tuns,” near the mouth of the river Bann on the north coast of Antrim

Tor Breogain:  “Bregon’s Tower,” in Spain

Tromma:  south-east of Cruachan; also the name of a river flowing into the
Boyne near Slane