| Főalak | Hány bejegyzésben szerepel | Egyéb névváltozatok | Előfordulás nem keltezési helyként |
| Caesareoforum | -> Késmárk |
| Caesareopolis | -> Késmárk |
| Caila | -> Cajla |
| Cajla (b) | 5 | Caila; Czaila; Czajla; Czayla; Zayla; Zeil |
| Calais (b) | 1 | Calesium; Caletum; Calisium |
| Calau | Kalau | 14008 |
| Calba | -> Calw |
| Calegia | -> Wittenberg |
| Calesium | -> Calais |
| Caletum | -> Calais |
| Calisium | -> Calais |
| Calorno | -> Colorno |
| Calw (b) | 4 | Calba | 10551 |
| Cambridge (b) | 74 | Cantabrigia | 1889 |
| Cameracum ad Albim | -> Kemberg |
| Campoveria | -> Veere |
| Cankov | -> Csánk |
| Cantabrigia | -> Cambridge |
| Carei | -> Nagykároly |
| Careii Mari | -> Nagykároly |
| Carinthia | -> Karintia |
| Carlostadium | -> Károlyváros |
| Carnovia | -> Krnov |
| Carolinum | -> Nagykároly |
| Carpathians | -> Kárpátok |
| Carpona | -> Korpona |
| Cartisoara | -> Kercisóra |
| Casellae | -> Kassel |
| Caslovice | -> Castalovice |
| Cassovia | -> Kassa |
| Castalovice (b) | 3 | Caslovice; Castolovice; Častolovice; Schaßlowitz |
| Castasegna (b) | 2 |
| Castolovice | -> Castalovice |
| Cavnic | -> Kapnikbánya |
| Cecejovce | -> Csécs |
| Cege (b) | 1 | Taga |
| Cekeháza (b) | 1 | Czekeháza |
| Celovce | -> Cselfalva |
| Cenabum | -> Orléans |
| Cerovo | -> Cseri |
| Certosa di Pavia (b) | 1 |
| Cervenica pri Sabinove | -> Vörösalma |
| Cesmarcum | -> Késmárk |
| Chalcedon | -> Khalkédón |
| Chemnitium | -> Chemnitz |
| Chemnitz | Chemnitium; Kemnitium | 3101; 6117; 15111 |
| Chilonium | -> Kiel |
| Chmelov | -> Komlóskeresztes |
| Chmeľovec | -> Tapolykomlós |
| Chojnów | Haynau | 14192 |
| Chur (b) | 13 | Curia Rhaetorum |
| Churkreis | -> Kurkreis |
| Chyzné | -> Hizsnyó |
| Cibinium | -> Nagyszeben |
| Cibinium | -> Kisszeben |
| Cícov | -> Csicsó |
| Cieszyn (b) | 9 | Teschen | 11563; 16664 |
| Cilicia | -> Kilikia |
| Cincu | -> Nagysink |
| Cincul Mare | -> Nagysink |
| Cinkota (b) | 3 |
| Cinobana | -> Szinóbánya |
| Cisa | -> Zeitz |
| Claudiopolis, Cluj | -> Kolozsvár |
| Clausthal (b) | 3 |
| Cleve | -> Kleve |
| Clèves | -> Kleve |
| Clivia | -> Kleve |
| Coburg (b) | 21 | 3013; 3444; 6326; 7242; 15745 |
| Codania | -> Koppenhága |
| Colberga | -> Kolobrzeg |
| Cölln | 7908; 7911 |
| Colmar | 10922 |
| Colonia Agrippina | -> Köln |
| Colonia Anniana | -> Nagyenyed |
| Colonia Brandenburgica | -> Kölln a. d. Spree |
| Colonia Ubiorum | -> Köln |
| Colophon | -> Kolophón |
| Colorno (b) | 2 | Calorno; Colurnum |
| Colurnum | -> Colorno |
| Comaromium | -> Komárom |
| Comburg (b) | 1 |
| Constadt | -> Wolczyn |
| Constantinopolis | -> Konstantinápoly |
| Copșa Mică | -> Kiskapus |
| Cornesti | -> Sövényfalva |
| Corona | -> Brassó |
| Costrinum | -> Küstrin |
| Coswig | 4882 |
| Cotha, Cothena | -> Köthen |
| Couronia | -> Kurzeme |
| Cremnic | -> Körmöcbánya |
| Cremona (b) | 4 |
| Crempis | -> Krempe |
| Creutzberga | -> Kreuzburg |
| Creuzburg | Cruciburgum ad Vierram | 14921 |
| Cricau | -> Boroskrakkó |
| Cronstadt | -> Brassó |
| Cruciburgum | -> Kreuzburg |
| Cruciburgum ad Vierram | -> Creuzburg |
| Crumlavia | -> Kromau |
| Crumlovium | -> Kromau |
| Crvenka | -> Cservenka |
| Csallóköz | Schütt; Zitny ostrov | 6333; 15841 |
| Csánk (b) | 3 | Cankov |
| Csécs (b) | 17 | Cecejovce |
| Csehország | Bohemia; Böhmen; Čechy | 174; 556; 559; 587; 610; 9961; 10192; 11113; 12721; 12750; 14061; 14078; 15071; 15094; 15444; 15591; 15685; 15789; 15932; 16383; 16387 |
| Csejte | Čachtice; Schächtitz | 9998 |
| Cseklész (b) | 2 | Bernolákovo; Čeklís; Landschütz; Lanschitz |
| Cselfalva (b) | 1 | Celovce | 2598 |
| Csenge | -> Csönge |
| Csepánfalva (b) | 2 | Stefansdorf; Stepanovce |
| Csepreg | 3783 |
| Cserepes | -> Pongyelok |
| Cserhátsurány (b) | 12 | Surány |
| Cseri (b) | 1 | Cerovo |
| Csermend (b) | 1 | Čermany; Tscherman |
| Csernye | -> Bakonycsernye |
| Cservenka (b) | 1 | Crvenka; Rotweil |
| Csetnek (b) | 29 | Stitnik |
| Csicsó (b) | 1 | Cícov |
| Csomád | 3352 |
| Csönge (b) | 4 | Csenge | 11609 |
| Csővár (b) | 10 | 10252; 10701 |
| Csurgó | 3886 |
| Curia Rhaetorum | -> Chur |
| Curia Variscorum | -> Hof (Saale) |
| Curlandia | -> Kurzeme |
| Curonia | -> Kurzeme |
| Custrinum | -> Küstrin |
| Cygnea | -> Zwickau |
| Cygneum | -> Zwickau |
| Cynavia | -> Zwickau |
| Czaila | -> Cajla |
| Czajla | -> Cajla |
| Czaplinek | Tempelburg | 16502 |
| Czayla | -> Cajla |
| Czekeháza | -> Cekeháza |
A helynévmutató 1561 helynevet tartalmaz.