| | | |
| Oak: Hatfield Broad Oak | Harlow Hundred | Essex, Volume 8 |
| Oakengates: Wombridge, later Oakengates | Bradford Hundred [Southern Division] | Shropshire, Volume 11 |
| Oakham: Hospital of St John Evangelist and St Anne at Oakham | Religious Houses | Rutland, Volume 1 |
| Oakham | Oakham Soke | Rutland, Volume 2 |
| Oakham Soke | | Rutland, Volume 2 |
| Oakham: Subsequent History of Oakham Grammar School | Schools | Rutland, Volume 1 |
| Oakham: The Grammar Schools of Oakham and Uppingham | Schools | Rutland, Volume 1 |
| Oakington | Northstowe Hundred | Cambridgeshire, Volume 9 |
| Oakley: Church Oakley | Chuteley Hundred | Hampshire, Volume 4 |
| Oakley: Corby and Great Oakley | [Corby Hundred] | Northamptonshire, Volume 7 |
| Oakley | Ashendon Hundred | Buckinghamshire, Volume 4 |
| Oakley | Stodden Hundred | Bedfordshire, Volume 3 |
| Oaksey | Malmesbury Hundred | Wiltshire, Volume 14 |
| Ock: Hundred of Ock | | Berkshire, Volume 4 |
| Ockendon: North Ockendon | Chafford Hundred | Essex, Volume 7 |
| Ockendon: South Ockendon | Chafford Hundred | Essex, Volume 7 |
| Ockham | Woking Hundred | Surrey, Volume 3 |
| Ockley | Wotton Hundred | Surrey, Volume 3 |
| Oddingley | Oswaldslow Hundred | Worcestershire, Volume 3 |
| Oddington | Ploughley Hundred | Oxfordshire, Volume 6 |
| Oddington | Slaughter Hundred | Gloucestershire, Volume 6 |
| Odell | Willey Hundred | Bedfordshire, Volume 3 |
| Odiham | Odiham Hundred | Hampshire, Volume 4 |
| Odiham Hundred | | Hampshire, Volume 4 |
| Odsey Hundred | | Hertfordshire, Volume 3 |
| Offchurch | Knightlow Hundred | Warwickshire, Volume 6 |
| Offenham | Blackenhurst Hundred | Worcestershire, Volume 2 |
| Offley | Hitchin Hundred | Hertfordshire, Volume 3 |
| Offlow Hundred (part) | | Staffordshire, Volume 17 |
| [Offlow Hundred] | | Staffordshire, Volume 9 |
| [Offlow Hundred] | | Staffordshire, Volume 12 |
| Offord Cluny | Toseland Hundred | Huntingdonshire, Volume 2 |
| Offord Darcy | Toseland Hundred | Huntingdonshire, Volume 2 |
| Ogbourne: 48. Priory of Ogbourne | The Religious Houses of Wiltshire | Wiltshire, Volume 3 |
| Ogbourne St Andrew | Selkley Hundred | Wiltshire, Volume 12 |
| Ogbourne St George | Selkley Hundred | Wiltshire, Volume 12 |
| Olave: Priory of Creeting St Olave | Religious Houses | Suffolk, Volume 2 |
| Old: Basing or Old Basing | Basingstoke Hundred | Hampshire, Volume 4 |
| Old alias Wold | Orlingbury Hundred | Northamptonshire, Volume 4 |
| Old Alresford | Fawley Hundred with the Liberty of Alresford | Hampshire, Volume 3 |
| Old and New Shoreham | Bramber Rape | Sussex, Volume 6, part 1 |
| Old Byland | Birdforth Wapentake | Yorkshire: North Riding, Volume 2 |
| Old Cleeve | Williton and Freemanors Hundred (eastern part) | Somerset, Volume 5 |
| Old Hurst | Hurstingstone Hundred | Huntingdonshire, Volume 2 |
| Old Malton | Richmondshire | Yorkshire: North Riding, Volume 1 |
| Old Stratford | Cleley Hundred | Northamptonshire, Volume 5 |
| Old Swinford with Stourbridge | Halfshire Hundred | Worcestershire, Volume 3 |
| Old Warden | Wixamtree Hundred | Bedfordshire, Volume 3 |
| Old Weston | Leightonstone Hundred | Huntingdonshire, Volume 3 |
| Old Wheatley and Coombe | Bullingdon Hundred | Oxfordshire, Volume 5 |
| Old Windsor | Ripplesmere Hundred | Berkshire, Volume 3 |
| Old Woodstock | Wootton Hundred (southern part) | Oxfordshire, Volume 12 |
| Old: Priory of Old Buckenham | Religious Houses | Norfolk, Volume 2 |
| Old: The Borough of Old Salisbury | | Wiltshire, Volume 6 |
| Old: The East: Old Ford Lane, Green Street, and Globe Town | Ossulstone Hundred (continued) | Middlesex, Volume 11 |
| Oldberrow | Blackenhurst Hundred | Worcestershire, Volume 2 |
| Oldberrow | Barlichway Hundred | Warwickshire, Volume 3 |
| Oldham Grammar School | Schools | Lancashire, Volume 2 |
| Oldham: Prestwich-with-Oldham | Salford Hundred (continued) | Lancashire, Volume 5 |
| Oliffe: Shipton Oliffe and Shipton Solers | Bradley Hundred | Gloucestershire, Volume 9 |
| Olney with Warrington | Newport Hundred | Buckinghamshire, Volume 4 |
| Ombersley | Oswaldslow Hundred | Worcestershire, Volume 3 |
| Onecote | Totmonslow Hundred (part) | Staffordshire, Volume 7 |
| Ongar: Chipping Ongar | Ongar Hundred | Essex, Volume 4 |
| Ongar: High Ongar | Ongar Hundred | Essex, Volume 4 |
| Ongar Hundred | | Essex, Volume 4 |
| Orcheston St Mary | Branch and Dole Hundred | Wiltshire, Volume 15 |
| Ore | The Rape and Honour of Hastings | Sussex, Volume 9 |
| Orford: Austin Friars of Orford | Religious Houses | Suffolk, Volume 2 |
| Orford: Hospitals of Orford | Religious Houses | Suffolk, Volume 2 |
| Orford: Priory of Orford | Religious Houses | Lincolnshire, Volume 2 |
| Orleton: Eastham with Hanley Child and Orleton | Doddingtree Hundred | Worcestershire, Volume 4 |
| Orlingbury | Orlingbury Hundred | Northamptonshire, Volume 4 |
| Orlingbury Hundred | | Northamptonshire, Volume 4 |
| Ormesby | Langbaurgh Wapentake (West) | Yorkshire: North Riding, Volume 2 |
| Ormsby: Priory of North Ormsby, or Nun Ormsby | Religious Houses | Lincolnshire, Volume 2 |
| Ormsby: Priory of North Ormsby, or Nun Ormsby | Religious Houses | Lincolnshire, Volume 2 |
| Ormskirk | West Derby Hundred | Lancashire, Volume 3 |
| Ormskirk Grammar School | Schools | Lancashire, Volume 2 |
| Orton Longueville with Botolphbridge | Norman Cross Hundred | Huntingdonshire, Volume 3 |
| Orton Waterville | Norman Cross Hundred | Huntingdonshire, Volume 3 |
| Orton: Water Orton | Hemlingford Hundred | Warwickshire, Volume 4 |
| Orwell | Wetherley Hundred | Cambridgeshire, Volume 5 |
| Osbaldwick | Bulmer Wapentake | Yorkshire: North Riding, Volume 2 |
| Oseney: Abbey of Oseney | Religious Houses | Oxfordshire, Volume 2 |
| Osgodby | Ouse and Derwent Wapentake | Yorkshire: East Riding, Volume 3 |
| Osmotherley | Richmondshire | Yorkshire: North Riding, Volume 1 |
| Ospringe: Hospital of Ospringe | Religious Houses | Kent, Volume 2 |
| Ossington: Preceptory of Ossington | Religious Houses | Nottinghamshire, Volume 2 |
| Ossulstone Hundred | | Middlesex, Volume 6 |
| Ossulstone Hundred (continued) | | Middlesex, Volume 11 |
| Ossulstone Hundred (continued) | | Middlesex, Volume 8 |
| Ossulstone Hundred (continued) | | Middlesex, Volume 9 |
| Ossulstone Hundred (continued) | | Middlesex, Volume 7 |
| Ossulstone Hundred (continued) | | Middlesex, Volume 10 |
| [Ossulstone Hundred] | | Middlesex, Volume 12 |
| Oswald: Hospital of St Oswald, Worcester | Religious Houses | Worcestershire, Volume 2 |
| Oswald: Priory of St Oswald, Gloucester | Religious Houses | Gloucestershire, Volume 2 |
| Oswaldkirk | Richmondshire | Yorkshire: North Riding, Volume 1 |
| Oswaldslow Hundred | | Worcestershire, Volume 3 |
| Oswestry: 27. Oswestry St John | Religious Houses | Shropshire, Volume 2 |
| Oswestry: 8. Oswestry School | Public Schools and Endowed Grammar Schools | Shropshire, Volume 2 |
| Osyth: Introduction: St Osyth to the Naze | St Osyth to the Naze: North-East Essex Coastal Parishes. Part 1: St Osyth, Great and Little Clacton, | Essex, Volume 12, part 1 |
| Osyth: St Osyth | St Osyth to the Naze: North-East Essex Coastal Parishes. Part 1: St Osyth, Great and Little Clacton, | Essex, Volume 12, part 1 |
| Osyth: St Osyth to the Naze: North-East Essex Coastal Parishes. Part 1: St Osyth, Great and Little Clacton, | | Essex, Volume 12, part 1 |
| Osyth: St Osyth to the Naze: North-East Essex Coastal Parishes. Part 1: St Osyth, Great and Little Clacton, | | Essex, Volume 12, part 1 |
| Osyth: St Osyth to the Naze: North-East Essex Coastal Parishes. Part 2. The Soken: Kirby-le-Soken, Thorpe-l | | Essex, Volume 12, part 2 |
| Osyth's: Abbey of Chich or St Osyth's | Religious Houses | Essex, Volume 2 |
| Otham: Abbey of Otham | Religious Houses | Sussex, Volume 2 |
| Other Great Driffield Townships | Harthill Wapentake, Bainton Beacon Division. Great Driffield and its Townships | Yorkshire: East Riding, Volume 9 |
| Othery | Whitley Hundred | Somerset, Volume 8 |
| Otmoor: Charlton-on-Otmoor | Ploughley Hundred | Oxfordshire, Volume 6 |
| Otterbourne | Buddlesgate Hundred | Hampshire, Volume 3 |
| Otterhampton | Cannington Hundred | Somerset, Volume 6 |
| Otterington: North Otterington | Richmondshire | Yorkshire: North Riding, Volume 1 |
| Otterington: South Otterington | Birdforth Wapentake | Yorkshire: North Riding, Volume 2 |
| Ottringham | Holderness Wapentake | Yorkshire: East Riding, Volume 5 |
| Oundle | Polebrook Hundred | Northamptonshire, Volume 3 |
| Ouse: Newton-upon-Ouse | Bulmer Wapentake | Yorkshire: North Riding, Volume 2 |
| Ouse and Derwent Wapentake | | Yorkshire: East Riding, Volume 3 |
| Ousebridge Maison Dieu, York | Religious Houses | Yorkshire: General, Volume 3 |
| Outer Tamworth (after Tamworth) | [Offlow Hundred] | Staffordshire, Volume 12 |
| Outwell and Upwell | Wisbech Hundred | Cambridgeshire, Volume 4 |
| Over | Papworth Hundred | Cambridgeshire, Volume 9 |
| Over Kellet School | Schools | Lancashire, Volume 2 |
| Over Norton | Chipping Norton and Area including Hook Norton and the Rollrights | Oxfordshire, Volume 21 |
| Over Silton | Birdforth Wapentake | Yorkshire: North Riding, Volume 2 |
| Over Stowey | Cannington Hundred | Somerset, Volume 6 |
| Over Wallop | Thorngate Hundred | Hampshire, Volume 4 |
| Over Whitacre | Hemlingford Hundred | Warwickshire, Volume 4 |
| Over Worton | Wootton Hundred | Oxfordshire, Volume 11 |
| Overblow: Collegiate Church of Kirkby Overblow | Religious Houses | Yorkshire: General, Volume 3 |
| Overbury with Alstone, Conderton, Teddington and Little Washbourne | Oswaldslow Hundred | Worcestershire, Volume 3 |
| Overstone | Spelhoe Hundred | Northamptonshire, Volume 4 |
| Overton: Market Overton | Alstoe Hundred | Rutland, Volume 2 |
| Overton | Overton Hundred | Hampshire, Volume 4 |
| Overton | Bulmer Wapentake | Yorkshire: North Riding, Volume 2 |
| Overton | Elstub and Everleigh Hundred | Wiltshire, Volume 11 |
| Overton Hundred | | Hampshire, Volume 4 |
| Overview: The South Oxfordshire Chilterns: An Overview | The South Oxfordshire Chilterns: Caversham, Goring, and Area | Oxfordshire, Volume 20 |
| Overy: Burton Overy | Gartree Hundred | Leicestershire, Volume 5 |
| Oving | The Rape of Chichester | Sussex, Volume 4 |
| Oving | Ashendon Hundred | Buckinghamshire, Volume 4 |
| Ovingdean | The Rape and Honour of Lewes | Sussex, Volume 7 |
| Ovington | Fawley Hundred with the Liberty of Alresford | Hampshire, Volume 3 |
| Owen's School | Schools | Middlesex, Volume 1 |
| Owslebury with Baybridge | Fawley Hundred with the Liberty of Alresford | Hampshire, Volume 3 |
| Owsthorpe: Sandholme with Owsthorpe and Hive | Howdenshire: the Townships | Yorkshire: East Riding, Volume 10, part 1 |
| Owston: Abbey of Owston | Religious Houses | Leicestershire, Volume 2 |
| Owston | Gartree Hundred | Leicestershire, Volume 5 |
| Owthorne | Holderness Wapentake | Yorkshire: East Riding, Volume 5 |
| Oxenhall | Newent and May Hill | Gloucestershire, Volume 12 |
| Oxenton | Tewkesbury Hundred, lower division | Gloucestershire, Volume 8 |
| Oxford: Canons of the Church of St George, Oxford | Religious Houses | Oxfordshire, Volume 2 |
| Oxford: Canterbury College, Oxford | Religious Houses | Oxfordshire, Volume 2 |
| Oxford: College of St Bernard, Oxford | Religious Houses | Oxfordshire, Volume 2 |
| Oxford: College of St George, Oxford | Religious Houses | Oxfordshire, Volume 2 |
| Oxford: Durham College, Oxford | Religious Houses | Oxfordshire, Volume 2 |
| Oxford: Gloucester College, Oxford | Religious Houses | Oxfordshire, Volume 2 |
| Oxford: Hospital of St Bartholomew, Oxford | Religious Houses | Oxfordshire, Volume 2 |
| Oxford: Hospital of St Clement, Oxford | Religious Houses | Oxfordshire, Volume 2 |
| Oxford: Hospital of St Giles, Oxford | Religious Houses | Oxfordshire, Volume 2 |
| Oxford: Hospital of St John the Baptist, Oxford | Religious Houses | Oxfordshire, Volume 2 |
| Oxford: Hospital of St Peter, Oxford | Religious Houses | Oxfordshire, Volume 2 |
| Oxford: Priory of St Frideswide, Oxford | Religious Houses | Oxfordshire, Volume 2 |
| Oxford: St Mary's College, Oxford | Religious Houses | Oxfordshire, Volume 2 |
| Oxford: The City of Oxford | | Oxfordshire, Volume 4 |
| Oxford: The University of Oxford | | Oxfordshire, Volume 3 |
| Oxford: [the following friars are of Oxford:] | Religious Houses | Oxfordshire, Volume 2 |
| Oxfordshire: The South Oxfordshire Chilterns: An Overview | The South Oxfordshire Chilterns: Caversham, Goring, and Area | Oxfordshire, Volume 20 |
| Oxfordshire: The South Oxfordshire Chilterns: Caversham, Goring, and Area | | Oxfordshire, Volume 20 |
| Oxhill | Kington Hundred | Warwickshire, Volume 5 |
| Oxted | Tandridge Hundred | Surrey, Volume 4 |