| Name/Location | County | Open | Close | Comment |
| ICENI, Ickburgh, Thetford | Norfolk | 1995 | . | . |
| IDLE, West Stockwith, Doncaster | Nottinghamshire | 2007 | . | Located at The White Hart Inn. Plant ex Broadstone |
| ILKLEY, Ilkley | W Yorkshire | 2009 | . | . |
| Imperial Arms | . | . | . | See Haggards |
| IND COOPE, Burton-upon-Trent | Staffordshire | 1856 | 1998 | Star Brewery. Formerly Samuel Allsops. Merged with Tetleys & Ansells 1961. Plant & site sold to Bass |
| IND COOPE, Romford | Essex | 1845 | 1992 | Star Brewery. Merged with Samuel Allsopp 1934. Merged with Tetleys & Ansells 1961. |
| Inn Brewing | . | . | . | See Berkhamstead |
| INNIS & GUNN, Edinburgh | Midlothian | No brewery | . | Specialist bottlers. Beers contract brewed by Caledonian |
| INNUENDO, Reading | Berkshire | 1998 | 1999 | Located at The Horse & Jockey PH. Acquired & closed by Greene King |
| Interbrew, Luton | Bedfordshire | . | . | The wholly-owned UK subsidiary of Inbev (Belgium). See also Interbrew Belfast, Glasgow, Magor, Manchester & Samlesbury |
| INTERBREW, Belfast | N I | Reg 1925 | ? | Formerly Thomas Caffrey & Son. Acquired by Charringtons (Bass) 1964 & by Interbrew 2000. Keg only |
| INTERBREW, Glasgow | Lanarkshire | Reg 1890 | . | Wellpark Brewery. Founded c1776. Acquired from Tennent-Caledonian by Charringtons (Bass) 1963 & by Interbrew 2000. Keg only since 1990 |
| INTERBREW, Magor | Monmouthshire | 1979 | . | Acquired from Whitbread 2000. Keg only |
| INTERBREW, Manchester | Gtr Manchester | 1788 | 2205 | Strangeways Brewery. Acquired by Boddingtons 1853, by Whitbread 1989 & by Interbrew 2000 |
| INTERBREW, Samlesbury | Lancashire | 1972 | . | Acquired from Whitbread 2000. Keg only |
| INVERALMOND, Inveralmond | Perthshire | 1997 | . | . |
| Iris Rose | . | . | . | See Newtonmore & Kingussie |
| IRISH, Newbridge, Co Kildare | Ireland | 1999? | . | . |
| IRONBRIDGE, Ironbridge, Telford | Shropshire | 2008 | . | . |
| IRONBRIDGE TAVERN, Limehouse | London E14 | 1980 | 1982 | . |
| IRVING, Portsmouth | Hampshire | 2007 | . | Plant part ex Teignworthy & Hobsons |
| Isca Ales Ltd | . | . | . | See Gargoyles |
| Island | . | . | . | See Burts (Newport) |
| ISLAND, Staveley, Newport | I o W | 2010 | . | Aka Isle of Wight Brewery |
| ISLAY ALES, Bridgend, Isle of Islay | Argyllshire | 2004 | . | . |
| Isle of Anglesey | . | . | . | See Ynys Mon |
| Isle of Arran | . | . | . | See Arran |
| ISLE of AVALON, Ashcott, Bridgewater | Somerset | No Brewery | Using Wessex plant until own operational | . |
| Isle of Man | . | . | . | See Okell |
| ISLE of MULL, Ledaig, Tobermory, Isle of Mull | Argyllshire | 2005 | 2009 | Plant sold to Oban Bay. May restart 2010 |
| ISLE of PURBECK, Studland, Swanage | Dorset | 2002 | . | Located at The Bankes Arms Hotel. Plant ex Brewhouse |
| ISLE of SKYE, Uig, Isle of Skye | Inverness-shire | 1995 | . | Aka Leann an Eilein |
| Isle of Wight | . | . | . | See Island |
| ITCHEN VALLEY, Arlesford | Hampshire | 1997 | . | Ceased briefly/ownership change 2000 |
| IVY BUSH, Edgbaston | W Midlands | 1994? | 1999 | Also a Brewers World DIY brewery |