| c | circa ('around', of dates) |
| C of E | Church of England |
| c/o | care of |
| CA | County Alderman; Chartered Accountant (Scotland and Canada); California |
| CAA | Civil Aviation Authority |
| CAAV | (Member of) Central Association of Agricultural Valuers |
| CAB | Citizens' Advice Bureau; Centre for Agricultural and Biosciences (formerly Commonwealth Agricultural Bureau) |
| CAER | Conservative Action for Electoral Reform |
| CAFOD | Catholic Fund for Overseas Development |
| Calif | California |
| CAM | Medal of the Order of Australia |
| Cambridge | Cambridge |
| Cambs | Cambridgeshire |
| Cantab | Cantabrigiensis (of Cambridge) |
| Capt | Captain |
| Cards | Cardiganshire |
| CARE | Cottage and Rural Enterprises |
| Carmarths | Carmarthenshire |
| CAS | Chief of the Air Staff |
| Cav | Cavalry |
| CB | Companion, Order of the Bath; County Borough |
| CBC | County Borough Council |
| CBE | Commander, Order of the British Empire |
| CBI | Confederation of British Industry |
| CBIM | Companion, British Institute of Management |
| CBiol | Chartered Biologist |
| CBS | Columbia Broadcasting System; Confraternity of the Blessed Sacrament |
| CC | County Council(lor); Companion, Order of Canada; City Council; Cricket Club; Cycling Club; County Court |
| CCAB | Consultative Committee of Accountancy Bodies |
| CCBE | Commission Consultative des Barreaux de la Coinmunaute Europeenne |
| CCC | Corpus Christ! College; Central Criminal Court; County Cricket Club |
| CCF | Combined Cadet Force |
| CCG | Control Commission Germany |
| CChem | Chartered Chemist |
| CCRA | Commander Corps of Royal Artillery |
| CCS | Casualty Clearing Station; Ceylon Civil Service; Countryside Commission for Scotland |
| CD | Civil Defence; Canadian Forces Decoration; Commander, Order of Distinction (Jamaica) |
| CDA | Co-operative Development Agency |
| CDipAF | Certified Diploma in Accounting and Finance |
| Cdr | Commander |
| Cdre | Commodore |
| CDS | Chief of the Defence Staff |
| CE | Civil Engineer |
| CEE | Communaute Economique Europeen |
| CEED | Centre for Economic and Environmental Development |
| CEF | Canadian Expeditionary Force |
| CEGB | Central Electricity Generating Board |
| CEMA | Council for the Encouragement of Music and Arts |
| CEMR | Council of European Municipalities and Regions |
| CEng | Chartered Engineer |
| Centl | Central |
| CEO | Chief Executive Officer |
| Cert | Certificate |
| CF | Chaplain to the Forces; Companion, Order of Fiji |
| CFA | Canadian Field Artillery |
| CFE | Central Fighter Establishment; College of Further Education |
| CFS | Central Flying School |
| CGA | Community of the Glorious Ascension; Country Gentlemen's Association |
| CGeol | Chartered Geologist |
| CGIA | Insignia Award of City and Guilds of London Institute |
| CGLI | City and Guilds of London Institute |
| CGS | Chief of the General Staff |
| CH | Companion of Honour |
| Ch Ch | Christ Church |
| ChB | Bachelor of Surgery (Chirurgy) |
| CHC | Community Health Council |
| Chllr | Chancellor |
| ChM | Master of Surgery |
| ChStJ | Chaplain, Most Venerable Order of the Hospital of St John of Jerusalem |
| CI | Imperial Order of the Crown of India; Channel Islands |
| CIA | Chemical Industries Association; Central Intelligence Agency |
| CIArb | Chartered Institute of Arbitrators |
| CIB | Chartered Institute of Bankers |
| CIC | Chemical Institute of Canada |
| CID | Criminal Investigation Department |
| CIE | Companion, Order of the Indian Empire; Confederation Internationale des Etudiants |
| CIGS | Chief of the Imperial General Staff |
| CIM | China Inland Mission |
| CIMA | Chartered Institute of Management Accountants |
| CIMgt | Companion, Institute of Management |
| CIPD | Companion, Institute of Personnel and Development |
| Civ | civil |
| CJ | Chief Justice |
| CL | Commander, Order of Leopold |
| CLA | Country Landowners' Association |
| CLit | Companion of Literature (Royal Society of Literature Award) |
| CLY | City of London Yeomanry |
| CM | Member, Order of Canada; Congregation of the Mission (Vincentians); Master in Surgery; Certificated Master; Canadian Militia |
| CMA | Canadian Medical Association; Cost and Management Accountant (NZ) |
| CMB | Central Midwives' Board |
| CMC | Certified Management Consultant |
| Cmd | Command (e.g., Southern Command) |
| cmded | commanded |
| cmdg | commanding |
| Cmdt | Commandant |
| CMF | Commonwealth Military Forces; Central Mediterranean Force |
| CMG | Companion, Order of St Michael and St George |
| CMLJ | Commander of Merit, Order of St Lazarus of Jerusalem |
| CMP | Corps of Military Police |
| CMS | Church Mission (formerly Church Missionary) Society; Certificate in Management Studies |
| CMZS | Corresponding Member, Zoological Society |
| CNAA | Council for National Academic Awards |
| Cncl | Council |
| Cncllr | Councillor |
| CND | Campaign for Nuclear Disarmament |
| CO | Commanding Officer; Commonwealth Office (after Aug 1966); Colonial Office (before Aug 1966): Conscientious Objector; Colorado |
| COHSE | Confederation of Health Service Employees |
| COI | Central Office of Information |
| Col | Colonel |
| Coll | College; Collegiate |
| Colo | Colorado |
| Commn | Commission |
| commnd | commissioned |
| Commr | Commissioner |
| CON | Officer, Order of the Niger |
| Conf | Conference |
| Conn | Connecticut |
| Const | Constitutional |
| COPUS | Committee on the Public Understanding of Science |
| Corp | Corporation |
| COS | Chief of Staff; Charity Organization Society |
| COSLA | Convention of Scottish Local Authorities |
| COSSAC | Chief of Staff to Supreme Allied Commander |
| CP | Central Provinces; Cape Province; Congregation of the Passion; Communist Party |
| CPA | Commonwealth Parliamentary Association; Chartered Patent Agent; Certified Public Accountant (Canada) |
| CPC | Conservative Political Centre |
| CPEng | Chartered Professional Engineer (of Institution of Engineers of Australia) |
| Cpl | Corporal |
| CPM | Colonial Police Medal |
| CPRE | Council for the Protection of Rural England |
| CPRS | Central Policy Review Staff |
| CPRW | Campaign for the Protection of Rural Wales |
| CPS | Crown Prosecution Service |
| CPsychol | Chartered Psychologist |
| CQSW | Certificate of Qualification in Social Work |
| CR | Community of the Resurrection |
| cr | created / creation |
| CRA | Commander, Royal Artillery |
| CRAeS | Companion, Royal Aeronautical Society |
| CRC | Cancer Research Campaign; Community Relations Council |
| CRE | Commander, Royal Engineers; Commission for Racial Equality; Commercial Relations and Exports |
| CREME | Commander, Royal Electrical and Mechanical Engineers |
| Cres | Crescent |
| CRO | Commonwealth Relations Office |
| CS | Civil Service; Clerk to the Signet |
| CSCE | Conference on Security and Co-operation in Europe |
| CSD | Civil Service Department; Co-operative Secretaries Diploma; Chartered Society of Designers |
| CSI | Companion, Order of the Star of India |
| CSIRO | Commonwealth Scientific and Industrial Research Organization (Australia) |
| CSM | Company Sergeant-Major |
| CSO | Chief Scientific Officer; Chief Signal Officer; Chief Staff Officer; Central Statistical Office |
| CSP | Chartered Society of Physiotherapists; Civil Service of Pakistan |
| CSS | Companion, Star of Sarawak; Council for Science and Society |
| CSSR | Congregation of the Most Holy Redeemer (Redemptorist Order) |
| CStJ | Commander, Most Venerable Order of the Hospital of St John of Jerusalem |
| CSV | Community Service Volunteers |
| CT | Connecticut |
| Ctee | Committee |
| CU | Cambridge University |
| CV | Cross of Valour (Canada) |
| CVCP | Committee of Vice-Chancellors and Principals of the Universities of the United Kingdom |
| CVO | Commander, Royal Victorian Order |
| CWA | Crime Writers Association |
| Cwlth | Commonwealth |
| CWS | Co-operative Wholesale Society |