| Maitland Valley Conservation Authority, Wroxeter | Howick |
| Maitland Valley Conservation Authority, Wroxeter, Middle Maitland Rejuvenation Committee | Howick |
| Maitland Valley Snowmobile Club | North Perth |
| March of Dimes Canada (GTA) | Toronto |
| Mary Hansen & Associates: Consulting Service - Rehabilitation , Vocational and Return to Work, No Physical Address | Goderich |
| Masonic Lodge, Listowel Masonic Hall, Bernard Lodge 225 | Listowel |
| Masonic Lodge, Mitchell, Tudor 141 A.F. & A.M. | Mitchell |
| Masonic Lodge, St Marys, St James-Tecumseh Masonic Lodge No. 73 | St Marys |
| McConnell Club | St Marys |
| McIntosh Farms, Listowel Butcher Shop | North Perth |
| MED-E-OX, Goderich, Medical Equipment & Home Respiratory Ltd | Goderich |
| MedicAlert Foundation Canada | North York East |
| Memorial Baptist Church, Kids' Church | Stratford |
| Memorial Baptist Church | Stratford |
| Mid Huron Minor Hockey Association, Mailing Address | Central Huron |
| Middlesex Swimming | Stratford |
| Millbank Thrift Store | Perth East |
| Milverton Agricultural Society, Milverton Agri Centre | Perth East |
| Milverton and District Medical Centre | Perth East |
| Milverton and District Minor Softball, Mailing Address | Perth East |
| Milverton and District Snowmobile Club | Perth East |
| Milverton Christian Fellowship | Perth East |
| Milverton Curling Club | Perth East |
| Mindful Kids Inc., Stratford | Stratford |
| Ministry of Children, Community and Social Services (MCCSS), Stratford, Ontario Disability Support Program | Stratford |
| Ministry of Natural Resources, Southern Region - Peterborough | Peterborough |
| Ministry of Tourism, Culture and Gaming and Ministry of Sport, Toronto | Toronto |
| Minor Hockey Alliance of Ontario | Stratford |
| Mitchell & District Agricultural Society | West Perth |
| Mitchell and Area Community Outreach, Congregate Dining & Social Programs | West Perth |
| Mitchell and Area Community Outreach, Meals on Wheels | West Perth |
| Mitchell and Area Community Outreach, Wellness / Exercise program | West Perth |
| Mitchell and Area Community Outreach, Volunteer Transportation | West Perth |
| Mitchell and Area Community Outreach, West Perth - Various Locations, Exercise and Falls Prevention Group program | West Perth |
| Mitchell and Area Community Outreach, West Perth Transit | West Perth |
| Mitchell Business Improvement Area | West Perth |
| Mitchell Curling Club | West Perth |
| Mitchell Family Doctors | West Perth |
| Mitchell Fish & Game Club | West Perth |
| Mitchell Gymnastics Club | Mitchell |
| Mitchell Horse Club | West Perth |
| Mitchell Legion Concert Band | West Perth |
| Mitchell Lions Club, Mailing Address Only | |
| Mitchell Lion's Park | West Perth |
| Mitchell Medical Pharmacy | Mitchell |
| Mitchell Minor Baseball | West Perth |
| Mitchell Minor Fastball | West Perth |
| Mitchell Minor Hockey | West Perth |
| Mitchell Minor Soccer | West Perth |
| Mitchell Minor Sports | West Perth |
| Mitchell Pioneer Hobby Association | West Perth |
| Mitchell Ringette | West Perth |
| Mitchell Skating Club, Mitchell Community Centre and Arena | West Perth |
| Mitchell Taxi | West Perth |
| Model Ts, St Marys, Men's Hockey | St Marys |
| Motherwell Women's Institute, St Marys - Mailing Address | Perth South |
| Multicultural Association of Perth-Huron | Stratford |
| Muscular Dystrophy Canada - Ontario Regional Office | Toronto Downtown North |
| Music and Opera Appreciation Inc, Music and Opera Appreciation | Stratford |
| My Grandfather's Cat, No Physical Address - Online Service | |