| # | Tower | No | Year | Materials | Maker | Trusses | Layout |
|---|
| 6401 | Olveston, Gloucestershire, S Mary V | 1 | 1907 | Composite | John Sully | 7.A.a ? | 8.3 |
| 6402 | Ombersley, Worcestershire, S Andrew | 1 | 1828 | Timber | ? Jacques family | 6.A & 6.I | 6.X |
| 6403 | Onibury, Shropshire, S Michael & All Angels | 1 | 1626 | Timber | | 6.A | 4.1 |
| 6404 | Orange, New South Wales, Australia, Holy Trinity | 1 | 2005 | Steel | Ron Shepherd | 8.1.B.a | 8.3 |
| 6405 | Orby, Lincolnshire, All Saints | 1 | 1921 | Steel | Mears & Stainbank | | |
| 6406 | Orchard Portman, Somerset, S Michael | 1 | 1746 | Oak | William Duck | | |
| 6407 | Orcheston, Wiltshire, S Mary | 1 | | Timber | | | |
| 6408 | Orcop, Herefordshire, S John Bapt | 1 | 1907 | Oak | William Greenleaf | 6.A | 5.X |
| 6409 | Ordsall, Nottinghamshire, All Hallows | 2 | 1892 | Cast iron | John Taylor & Co | | |
| 6410 | Ordsall, Nottinghamshire, All Hallows | 1 | 1892 | Cast iron | John Taylor & Co | 8.3.C.e | 5.4 |
| 6411 | Orford, Suffolk, S Bartholomew | 2 | 1915 | Timber | George Day & Sons | 6.D | 2.X1 |
| 6412 | Orford, Suffolk, S Bartholomew | 1 | 1998 | Cast iron & steel | Eayre & Smith | 8.2.A.b | 8.3 |
| 6413 | Orleans, Massachusetts, United States of America, The Transfiguration | 1 | 2009 | Steel | Whitechapel Bell Foundry | 8.1.B.c | 10.4 |
| 6414 | Orleton, Herefordshire, S George | 1 | | Oak | | | 4 |
| 6415 | Orlingbury, Northamptonshire, S Mary | 1 | c1843 | Oak | Local labour/guild/assn | 6.A | 4.X ➔ ~ 6.5 |
| 6416 | Orlingbury, Northamptonshire, S Mary | 1.1 | 1993 | Cast iron | John Taylor & Co | 8.3.A.h | 2.X1 |
| 6417 | Ormesby, North Yorkshire, S Cuthbert | 2 | 1908 | Cast iron | John Taylor & Co | 8.3.D.a | 4.2 |
| 6418 | Ormesby, North Yorkshire, S Cuthbert | 1 | 1908 | Cast iron | John Taylor & Co | 8.3.D.a | 4.2 |
| 6419 | Ormskirk, Lancashire, S Peter & S Paul | 8 | | | | | |
| 6420 | Ormskirk, Lancashire, S Peter & S Paul | 1 | | Oak | | 6.A | 8.3 |
| 6421 | Orsett, Essex, S Giles & All Saints | 1 | 1791 | Oak | | 6.A | 6.1 |
| 6422 | Orston, Nottinghamshire, S Mary | 1 | 1923 | Cast iron | Gillett & Johnston | | |
| 6423 | Orton Waterville, Cambridgeshire, S Mary | 1 | <1709 | Oak | | 6.A | 4.3 |
| 6424 | Orwell, Cambridgeshire, S Andrew | 1 | 1931 | Cast iron | John Taylor & Co | | 6 |
| 6425 | Osbournby, Lincolnshire, S Peter & S Paul | 1 | | Timber | | | 3 D |
| 6426 | Osmotherley, North Yorkshire, S Peter | 1 | | Timber | | 6.A & 6.B | 3.1 |
| 6427 | Ossett, West Yorkshire, Holy & Undivided Trinity | 2 | 2012 | Cast iron & steel | | | |
| 6428 | Ossett, West Yorkshire, Holy & Undivided Trinity | 1 | 1865 | Oak | John Taylor & Co | | |
| 6429 | Ossett, West Yorkshire, Holy & Undivided Trinity | 1.1 | 1935 | Oak | John Taylor & Co | | |
| 6430 | Ossett, West Yorkshire, Holy & Undivided Trinity | 1.2 | 1987 | Cast iron | Fred Pembleton | | |
| 6431 | Ossington, Nottinghamshire, Holy Rood | 2 | 1979 | Steel | Local labour/guild/assn | | |
| 6432 | Ossington, Nottinghamshire, Holy Rood | 1 | 1979 | Steel | Local labour/guild/assn | | |
| 6433 | Osterley, Greater London, S Mary, Osterley Road | 1 | | Timber | | | |
| 6434 | Oswaldkirk, North Yorkshire, S Oswald | 1 | c1886 | Oak | | 6.A | 2.X1 |
| 6435 | Oswaldtwistle, Lancashire, Immanuel | 1 | 1913 | Cast iron | John Taylor & Co | | |
| 6436 | Oswestry, Shropshire, S Oswald K&M | 1 | | Timber | | | 8.3 |
| 6437 | Otford, Kent, S Bartholomew | 1 | 2000 | Cast iron | Whitechapel Bell Foundry | 8.3.A.h | 6.1 |
| 6438 | Otham, Kent, S Nicholas | 1 | 1906 | Oak | Mears & Stainbank | 6.A | 3.1 ➔ 6.1 |
| 6439 | Otham, Kent, S Nicholas | 1.1 | 2012 | Steel | John Taylor & Co | 8.1.B.a | 2.X2 |
| 6440 | Otham, Kent, S Nicholas | 1.2 | 2012 | Steel | John Taylor & Co | | 1 |
| 6441 | Othery, Somerset, S Michael | 1 | 1860 | Oak | Henry Boswell | | |
| 6442 | Otley, Suffolk, S Mary | 1 | 1933 | Timber | Locally manufactured | 6.A | 6.5 R |
| 6443 | Otley, West Yorkshire, All Saints | 1 | 1922 | Cast iron | Gillett & Johnston | 8.3.C.e | 8.3 |
| 6444 | Otterford, Somerset, S Leonard | 1 | 1904 | Cast iron & timber | Thomas Doble | 7.A.a | 6.X |
| 6445 | Otterham, Cornwall, S Denis | 1 | 1953 | Cast iron | John Taylor & Co | 8.3.A.h | 6.X |
| 6446 | Otterhampton, Somerset, All Saints | 1 | † | Oak | | | |
| 6447 | Ottershaw, Surrey, Christ Church | 2 | 1885 | Cast iron | John Taylor & Co | 8.3.C.b | 2.X1 |
| 6448 | Ottershaw, Surrey, Christ Church | 1 | 1885 | Cast iron | John Taylor & Co | 8.3.C.b | 4.2 |
| 6449 | Otterton, Devon, S Michael | 2 | 1890 | Oak | Harry Stokes | 6.A | |
| 6450 | Otterton, Devon, S Michael | 1 | 1865 | Oak | Thomas I Hooper | 6.D | 5.12 |