| Leamington Spa observatory | Royal Leamington Spa | — |
| Lerwick Magnetic Observatory | Islas Shetland | — |
| Leyland Observatory | South Ribble | — |
| Liverpool observatory (before 1867) | Liverpool | — |
| Liverpool observatory (since 1867) | Liverpool | — |
| Loudwater observatory | Loudwater | — |
| Macclesfield observatory | Macclesfield | — |
| Macnairston Observatory | South Ayrshire | — |
| Maidenhead observatory | Windsor y Maidenhead | — |
| Makerstoun Observatory | Scottish Borders | — |
 Marina Towers Observatory | Swansea | — |
| Meridian Pillars, Brisbane House | North Ayrshire | — |
| Meridian Sitings | Tullyard | — |
| Mickleover observatory | Mickleover | — |
| Moon Palace | — | — |
 Moon Palace | — | — |
| Mount Tuffley Observatory | Gloucester | — |
| Mr. Barclay’s observatory | Essex | — |
 Mullard Radio Astronomy Observatory | Harlton | — |
| National Centre for Earth Observation | — | — |
| Newcastle-upon-Tyne observatory | Newcastle upon Tyne | — |
| NNHS Drummonds Observatory | Pitsford | — |
 Norman Lockyer Observatory | Sidmouth | — |
| North Observatory | Waterlooville | — |
 North Ronaldsay Bird Observatory | Orcadas | — |
| Northolt Branch Observatories | — | — |
| Northolt Branch Observatory | Municipio de Ealing | — |
| Northolt Branch Observatory 2 | Hammersmith y Fulham | — |
| Northolt Branch Observatory 3 | Blandford Forum | — |
| Nottingham Weather Centre | — | — |
 Nuffield Radioastronomy Laboratory | — | — |
 Observatorio de Armagh | Armagh | — |
 Observatorio de Cambridge | Cambridge | — |
 Observatorio de Isaac Roberts | Crowborough | 268 m |
 Observatorio George Bishop | Ciudad de Westminster | — |
 Observatorio Jodrell Bank | Lower Withington | 77 m |
| Observatorio Macfarlane | Escocia | — |
 Observatorio Mills | Dundee City | — |
 Observatorio Radcliffe | Oxford | — |
 Observatorio Vulcanológico de Montserrat | Plymouth | — |
 Observatory | distrito metropolitano de Oldham | — |
| Observatory At South Wing, St Ibbs, 90 Metres To West South West Of House | St Ippolyts | — |
| Observatory Circa 100 Yards South West Of Lilburn Tower | Lilburn | — |
 Observatory House | — | — |
| Observatory, Kinpurney Hill | Angus | — |
 Observatory, Museum Gardens | City of York | — |
| Observatory, Pitfour House Estate | Aberdeenshire | — |
| Octagon Observatory, Invercauld Road, Braemar | Aberdeenshire | — |