Chapman County Codes are commonly used in identifying administrative divisions in the United Kingdom, Ireland, the Isle of Man and the Channel Islands, but covering historical divisions. They were created by Dr Colin Chapman in the late 1970s, and are widely used in genealogy.
| BDF | Bedfordshire | HRT | Hertfordshire | SOM | Somersetshire |
| BRK | Berkshire | HUN | Huntingdonshire | STS | Staffordshire |
| BKM | Buckinghamshire | KEN | Kent | SFK | Suffolk |
| CAM | Cambridgeshire | LAN | Lancashire | SRY | Surrey |
| CHS | Cheshire | LEI | Leicestershire | SSX | Sussex |
| CON | Cornwall | LIN | Lincolnshire | WAR | Warwickshire |
| CUL | Cumberland | LND | London | WES | Westmorland |
| DBY | Derbyshire | MDX | Middlesex | WlL | Wiltshire |
| DEV | Devonshire | NFK | Norfolk | WOR | Worcestershire |
| DOR | Dorsetshire | NTH | Northamptonshire | YKS | Yorkshire |
| DUR | Durham | NBL | Northumberland | ERY | Yks East Riding |
| ESS | Essex | NTT | Nottinghamshire | WRY | Yks West Riding |
| GLS | Gloucestershire | OXF | Oxfordshire | NRY | Yks North Riding |
| HAM | Hampshire | RUT | Rutland | IOW | Isle of Wight |
| HEF | Herefordshire | SAL | Shropshire | IOM | Isle of Man |