Claimants
- Cadwalader
- Cadwell
- Caffrey
- Cahalan
- Cahilane
- Cahill
- Cairnes
- Cairns
- Caldwell
- Callaghan
- Callan
- Callanan
- Callender
- Calvert
- Calwell
- Cameron
- Cameron Sillar
- Campbell
- Camrass
- Canavan
- Cannon
- Canon
- Cant
- Cantley
- Canton
- Cantwell
- Carberry
- Carbery Evans
- Carden
- Caren
- Carew
- Carey
- Carins
- Carleton
- Carlton
- Carmichael
- Carnell
- Carney
- Carolan
- Carolin
- Carpenter
- Carr
- Carr Ellison
- Carre
- Carrick
- Carrigan
- Carroll
- Carson
- Cartan
- Carter
- Carton
- Carty
- Carver
- Casey
- Cashman
- Caslin
- Cassidy
- Casson
- Cathcart Hemphill
- Catterson
- Catterson Smith
- Caul
- Caulfield
- Caulfield Orpen
- Cave
- Cavey
- Chamberlaine
- Chambers
- Chamney
- Champ
- Chance
- Chancellor
- Chandler
- Chanler
- Chapman
- Charde
- Charles
- Charters
- Chartres
- Chase
- Chatfield
- Chevers
- Child
- Chillingworth
- Christian
- Christie
- Claffey
- Clampett
- Clancy
- Clark
- Clarke
- Clarke Whyte
- Clarkin
- Clavin
- Clayson
- Clayton MacDonald
- Cleane
- Cleary
- Cleere
- Clements
- Clerkin
- Clery
- Clinch
- Clinton Gough
- Clohessy
- Clohesy
- Clune
- Coates
- Coath
- Cobbe
- Cochrane
- Cockburn MacDonald
- Cockshaw
- Cocles Cooper
- Codd
- Coffey
- Cogan
- Coghlan
- Cohen
- Colbert
- Cole
- Coleman
- Colleary
- Colles
- Colley
- Colley Pounder
- Collier
- Collins
- Collis
- Colman
- Colohan
- Colvill McClintock Jones
- Colville McClintock Jones
- Comerford
- Companyne
- Conan
- Condon
- Condron
- Conlan
- Conlon
- Connell
- Connolly
- Connor
- Conran
- Conroy
- Conry
- Considine
- Constable
- Constantine
- Conway
- Conway Murphy
- Conyers
- Coogan
- Cook
- Cooke
- Cookman
- Coonan
- Cooney
- Cooper
- Coorhean
- Corballis
- Corbett
- Corcoran
- Cordner
- Corkery
- Corliss
- Corn
- Cornwall
- Corrigan
- Corringham
- Corry
- Cosgrave
- Cosgrove
- Coss
- Costello
- Cottell
- Cotter
- Cotton
- Coughlan
- Coughlin
- Coulson
- Coulter
- Counihan
- Courtney
- Coutts
- Cowan
- Cowle
- Cowley
- Cox
- Coyle
- Coyne
- Crabtree
- Craig
- Craigie
- Craine
- Crampton Walker
- Cran
- Cranny
- Crawford
- Crawley
- Crawshay Heyworth
- Creagh
- Crealock
- Creamer
- Crean
- Cree
- Creedon
- Cregan
- Creighton
- Creyne
- Crilly
- Crimmins
- Crinion
- Crofton
- Crofts
- Croke
- Croken Woodroffe
- Croly
- Crombie
- Cromien
- Cronin
- Crooks
- Crosbie
- Crosby
- Croskerry
- Crossan
- Crotty
- Crowe
- Crowley
- Cruden
- Cruise
- Cruise O'Brien
- Crummins
- Cryer
- Cuddihy
- Cuddy
- Cudlipp
- Cuff
- Culhane
- Cull
- Cullen
- Culverwell
- Cumisky
- Cummins
- Cuneo
- Cunningham
- Cunnion
- Curley
- Curran
- Currie
- Curry
- Curtin
- Curtis
- Cusack
- Cussen
- Cuthbert
- Cuthbertson