| Macaulay Tree House Day Nursery | Bracebridge |
| MacLaren Art Centre, Art Classes and Day Camps for Children and Youth | Barrie |
| MacLaren Art Centre | Barrie |
| MADD Canada, Mailing Address, Barrie Simcoe Chapter | Barrie |
| Make-A-Wish, Ontario Chapter | Pickering |
| Making Change, Mailing Address | Barrie |
| Manito Shriner's Club | Clearview (Simcoe County) |
| Maplehill Wellness, Barrie, Foot Care | Barrie |
| Maplehill Wellness | Wasaga Beach |
| Mapleview Community Church, Barrie | Barrie |
| March of Dimes Canada, Barrie - Bryne Dr, Brain Injury Services - Outreach Activity Groups in Simcoe County | Barrie |
| March of Dimes Canada, Collingwood, Assisted Living Services and Low Acuity Services - Community Support Services Program | Collingwood |
| March of Dimes Canada, Homemaking Services, Collingwood | Collingwood |
| March of Dimes Canada, Midland, Assisted Living Services and Low Acuity Services - Community Support Services Program | Midland |
| March of Dimes Canada, Midland, Homemaking Services | Midland |
| March Of Dimes Canada - Midland, Midland, Community Support Services | Midland |
| March of Dimes Canada (GTA) | Toronto |
| Marchmont Baptist Church, Severn | Severn |
| Mariposa Grandmothers for Stephen Lewis Foundation (SLF) | Orillia |
| Mariposa House Hospice | Severn |
| Mariposa Place | Orillia |
| Marlene's Foot Care | Clearview (Simcoe County) |
| Math3ma Academy | Barrie |
| Matthews House, Hospice Services - Our Residential Services | New Tecumseth |
| May Court Club of Barrie | Barrie |
| May Court Club of Barrie, Barrie | Barrie |
| May Court Club of Barrie, Barrie, May Court Shop | Barrie |
| McQuaig (Wendy), Orillia, Registered Psychotherapist | Orillia |
| Meadow Creek Montessori School, Barrie - Cundles Rd E, Meadow Creek Montessori School - East | Barrie |
| Meadow Creek Montessori School, Barrie - Ferndale Dr N, Meadow Creek Montessori School - West | Barrie |
| Meadow Creek Montessori School, Shanty Bay, Meadow Creek Montessori School - The Bay | Oro-Medonte |
| Meals On Wheels, Alliston | New Tecumseth |
| Meaningful Movement, Mobile Service, In-Home Physiotherapy | Barrie |
| Mediation Centre of Simcoe County | Barrie |
| MedicAlert Foundation Canada | North York East |
| Meeting Place (The), Orillia | Orillia |
| Mermigis (Dr Lambros) Psychologist | Barrie |
| Mete (Laurie Ann), Certified Advanced Foot Care | Springwater |
| Métis Nation of Ontario, Barrie Office, Infinity Property Services - Rural Urban Indigenous Housing Program | Barrie |
| Métis Nation of Ontario - Georgian Bay Council - Midland, Education and Training, Midland | Midland |
| Métis Nation of Ontario - Georgian Bay Council - Midland, Healing and Wellness Program, Midland | Midland |
| Métis Nation of Ontario - Georgian Bay Council - Midland, Metis Healthy Babies, Healthy Children, Midland | Midland |
| Midhurst Ratepayers' Association | Springwater |
| Midland Civitan Club, Midland | Midland |
| Midland Community Gardens, Midland Community Garden | Midland |
| Midland Horticultural Society | Midland |
| Midland Midwives By the Bay | Midland |
| Midland Midwives By the Bay, Georgian Bay General Hospital | Midland |
| Midland Mountainview Family Co-operative, Midland | Midland |
| Midland Public Library, Food Pantry | Midland |
| Midland Public Library | Midland |
| Midland Town Crier | Midland |
| Midland, Town of., Community Reach, Accessible Transit Service | Midland |
| Midland, Town of., Midland Penetanguishene Transit Service | Midland |
| Midland, Town of., Midland - Bayshore Dr, Fire Department | Midland |
| Midland, Town of., Midland - Dominion Ave, Municipal Office | Midland |
| Midland, Town of., Midland - Len Self Blvd - NSSRC, North Simcoe Sports and Recreation Centre | Midland |
| Midland, Town of., Midland Seniors Council, Midland - Len Self Blvd - NSSRC | Midland |
| Midland, Town of., No physical address, Rest Stations for Extreme Weather Relief | Midland |
| Midland-Penetanguishene District Community Emergency Response Team, Colborn St | Penetanguishene |
| Midwives Nottawasaga | Collingwood |
| Mill Creek Care Centre, Long Term Care Facility | Barrie |
| Ministry of Tourism, Culture and Gaming and Ministry of Sport, Barrie, Ontario Travel Information Centre | Barrie |
| Ministry of Tourism, Culture and Gaming and Ministry of Sport, Midhurst Office, Grants Administration and Community Development | Springwater |
| Ministry of Tourism, Culture and Gaming and Ministry of Sport, Midhurst Office, Tourism Regional Office | Springwater |
| Ministry of Tourism, Culture and Gaming and Ministry of Sport, Toronto | Toronto |
| Mirror (The) | Midland |
| Mission Thrift Store - Barrie | Barrie |
| Mnjikaning Fish Fence Circle | Orillia |
| Mobicare Advanced Foot Care | Barrie |
| Mobile Footcare Service, Bring Joy 2 Your Feet | Penetanguishene |
| Mobile Soup Kitchen, Community Pantry | Collingwood |
| Mobile Soup Kitchen | Collingwood |
| Modern College of Hairstyling and Esthetics | Barrie |
| Modern Healthcare Services | Innisfil |
| Mom's 4 Mom's Doula Services, No Physical Address | Oro-Medonte |
| Monarchist League Barrie Huronia Branch | |
| Mood Disorders Association of Ontario, Telephone Support Line | Toronto Downtown |
| Mortgage Centre (The), Christmas Hamper Program | Collingwood |
| MS Canada | Toronto |
| MTM Conservation Association, Tiny Marsh Nature Centre, Tiny Marsh Provincial Wildlife Area | Tiny |
| Mulcaster Mews | Barrie |
| Multiple Births Canada | Richmond Hill |
| MultiSport Canada | Barrie |
| Murray's Windermere Gardens | Barrie |
| Muscular Dystrophy Canada - Ontario Regional Office | Toronto Downtown North |
| Museum on the Boyne | New Tecumseth |
| Music Therapy Services of Simcoe County, Barrie | Barrie |
| Muskoka Ambulance Communications Service | Bracebridge |
| Muskoka Drug Strategy Coalition | Barrie |
| Muskoka Lakes Preschool | Muskoka Lakes Township |
| Muskoka North Residential | Gravenhurst |
| Muskoka Residential Centre | Severn |
| Muskoka Taxi | Gravenhurst |
| My Friend Beth Senior & Support Services, Collingwood | Collingwood |
| My Friend's House, Domestic Violence Shelter | Collingwood |
| My Pre Academy | Barrie |
| My Sister's Place | New Tecumseth |