| MacDonald's Landscaping | Collingwood |
| MacLaren Art Centre, Cours d'art et camps de jour pour enfants et jeunes | Barrie |
| MacLaren Art Centre, Centre d'art MacLaren | Barrie |
| MacTier Food Bank, MacTier, Banque alimentaire de MacTier | Georgian Bay Township |
| Madeline's Mobile Hair Care, Aucune adresse physique, Soins des cheveux mobile de Madeline | Orillia |
| Magic of Children in the Arts, Magie des enfants dans les arts | Collingwood |
| Maing (Dr Dianne) Psychologue | Barrie |
| Mains LeReseaudaideauxfamilies.ca, Inactif Bureau de Parry Sound, Bureau de Parry Sound | Parry Sound |
| Maison de retraite Champlain Manor | Orillia |
| Maison de retraite Terrace Simcoe | Barrie |
| Maisons coopératives Angus | Essa |
| Making Change, Aucune adresse physique | Barrie |
| Manito Shriner's Club | Clearview (Comté Simcoe) |
| Manna Food Bank of Bracebridge, Banque alimentaire Manna de Bracebridge | Bracebridge |
| Maplehill Wellness, Barrie, Soin des pieds | Barrie |
| Maplehill Wellness | Wasaga Beach |
| Mapleview Medical Pharmacy, Pharmacie médicale Mapleview | Barrie |
| Maplewood Retirement Residence, Résidence de retraite Maplewood | Penetanguishene |
| March of Dimes Canada, Barrie, Services de lésion cérébrale acquis - Groupes d'activités de sensibilisation dans le comté de Simcoe | Barrie |
| March of Dimes Canada, Mailing Address - Barrie and York Region, Programme d'amitié | Richmond Hill |
| March Of Dimes Canada, Penetanguishene, Programmes de vie autonome | Midland |
| Marche des dix sous Canada | Toronto |
| Marché des fermiers Orillia | Orillia |
| Marché fermier de Barrie | Barrie |
| Marek (Dr Ken) Psychologist Lifegates Unlimited, Dr Ken Marek, Psychologue | Barrie |
| Mariposa Folk Foundation, Fondation Mariposa Folk | Orillia |
| Mariposa Gymnastics Club | Orillia |
| Mariposa Place, Place Mariposa | Orillia |
| Marlene's Foot Care | Clearview (Comté Simcoe) |
| Martyrs' Shrine | Midland |
| Matheson Chiropratic Clinic, Orillia | Orillia |
| Matthews House, Unité de soins palliatifs communautaire | New Tecumseth |
| Matthews House Hospice, Soins palliatifs résidentiels | Alliston |
| Maximum Mobility Access Centre, Centre d'accès Maximum Mobility | Orillia |
| May Court Club of Barrie | Barrie |
| May Court Club of Barrie, Club May Court de Barrie | Barrie |
| May Court Club of Barrie, Magasin May Court | Barrie |
| McDermid (Pamela), Collingwood, Travailleuse sociale autorisée | Collingwood |
| Meadow Creek Montessori School, East, Meadow Creek Montessori School, Meadow Creek Montessori School East | Barrie |
| Meadow Creek Montessori School, West, Meadow Creek Montessori School, Meadow Creek Montessori School East | Barrie |
| Meals On Wheels, Alliston, Popote roulante | New Tecumseth |
| Meaningful Movement, Service mobile, Physiothérapie à domicile | Barrie |
| Mediation Centre of Simcoe County, Centre de médiation du comté de Simcoe | Barrie |
| Meeting Place (The), Orillia, Lieu de rencontre (Le) | Orillia |
| Mens Industrial Dart League, ligue de fléchettes pour hommes Industrial | Collingwood |
| Mermigis (Dr Lambros) Psychologist | Barrie |
| Mete (Laurie Ann), Soins avancés des pieds certifiés | Springwater |
| Metis Nation of Ontario, Bureau de Barrie, Services domiciliaires Infinity - Programme de logement rural autochtone | Barrie |
| Métis Nation of Ontario, Éducation et formation, Midland, Midland | Midland |
| Métis Nation of Ontario, Metis Healthy Babies, Healthy Children, Midland | Midland |
| Métis Nation of Ontario, Programme de ressourcement pour le mieux-être des Autochtones, Midland, Midland | Midland |
| Michela McConnell Psychotherapy & Consulting Services, Orillia, Psychothérapie et service de conseil | Orillia |
| Midhurst Ratepayers' Association, Association des contribuables Midhurst | Springwater |
| Midland Alliance Church, Église Midland Alliance | Midland |
| Midland and District Business Women's Association, Association des femmes d'affaires de Midland et district | Midland |
| Midland Bay Sailing Club, Club nautique Midland Bay | Midland |
| Midland Community Gardens, Midland Community Garden, Jardins communautaires de Midland | Midland |
| Midland Cultural Centre Inc | Midland |
| Midland District Camera Club, Club caméra de Midland et District | Midland |
| Midland Duplicate Bridge Club | Midland |
| Midland Hearing Centre, Midland | Midland |
| Midland Hiking Club | Midland |
| Midland Horticultural Society, Société horticole Midland | Midland |
| Midland Lions Club | Midland |
| Midland Minor Lacrosse Association, Huronia Braves Lacrosse | Midland |
| Midland Mountainview Family Co-operative, Inc, Midland Mountainview Family Co-operative Inc | Midland |
| Midland Physiotherapy and Rehabilitation Centre | Midland |
| Midland Power Utility Corporation | Midland |
| Midland Public Library, Bibliothèque publique de Midland Public Library | Midland |
| Midland Shuffleboard Club | Tay |
| Midland Small Set Co-op Nursery School, École maternelle coopérative Midland Small Set | Midland |
| Midland Sports Hall of Fame, Panthéon des sports Midland | Midland |
| Midland Town Crier, Crieur public de Midland | Midland |
| Midland, Penetanguishene and District Builders Association, Association des constructeurs de Midland, Penetanguishene et district | Midland |
| Midland, Town of., Community Reach, Service de transport accessible | Midland |
| Midland, Town of., Conseil des aînés de Midland, Midland - boulevard Len Self | Midland |
| Midland, Town of., Midland - Bayshore Dr, Service d'incendie | Midland |
| Midland, Town of., Midland - boulevard Len Self, North Simcoe Sports and Recreation Centre | Midland |
| Midland, Town of., Midland - Dominion Ave, Bureau municipal | Midland |
| Midland, Town of., parc Pete Petersen , Mise à l'eau publique | Midland |
| Midland, Town of., Midland - King St, Port de Midland | Midland |
| Midwives Nottawasaga | Midland |
| Midwives Nottawasaga, Midland Midwives By the Bay, Sages-femmes Midland Midwives By the Bay | Midland |
| Minesing Minor Ball Association, Association de balle mineure de Minesing | Springwater |
| Minesing United Church, Église Unie Minesing | Minesing |
| Ministère du Solliciteur général, Orillia, Probation et libération conditionnelle, Orillia | Orillia |
| Mission Thrift Store - Barrie, Friperie Mission - Barrie | Barrie |
| Mnjikaning Arena Sports Ki | Première Nation Chippewas de Rama |
| Mnjikaning Fish Fence Circle | Orillia |
| Modern College of Hairstyling and Esthetics, Collège moderne de coiffure et d'esthétique | Barrie |
| Molson Sportsmen Hockey League, ligue de hockey Molson Sportsmen | Barrie |
| Mom's 4 Mom's Doula Services, Pas d'adresse physique, Service de doula Mom's 4 Mom's Doula Services | Oro-Medonte |
| Monday Nights Dart League, Ligue de fléchettes du lundi soir | Collingwood |
| Mood Disorders Association of Ontario | Toronto |
| Morgentaler Clinic (The) | Toronto Centre-ville Nord |
| Mortgage Centre (The), Programme de paniers de Noël | Collingwood |
| Moulin Microcrédits, Bureau de Toronto | Toronto |
| Mountain Momma Collective, Ltd, Soutien en matière de naissance et de postpartum | Barrie |
| Mouvement pour la représentation équitable au Canada, Adresse postale, Section du comté de Simcoe | Barrie |
| MTM Conservation Association Incorporated, MTM Conservation Association, Réserve faunique provinciale de Tiny Marsh | Tiny |
| Mulcaster Mews | Barrie |
| Multiple Births Canada, Naissances multiples Canada | Richmond Hill |
| MultiSport Canada | Barrie |
| Murray's Windermere Gardens | Barrie |
| Musée centenaire et Archives de Penetanguishene, Penetanguishene Centennial Museum | Penetanguishene |
| Musée Coldwater | Severn |
| Musée Huronia et village Huron-Ouendat | Midland |
| Musée Huronia et village Huron-Ouendat, Programmes de camps de jour et de vacances | Midland |
| Musée militaire de la Base Borden | Adjala-Tosorontio |
| Museum on the Boyne | New Tecumseth |
| Music Therapy Services of Simcoe County, Services de musicothérapie du comté de Simcoe | Barrie |
| Muskoka Algonquin Healthcare, Emplacement de l'hôpital South Muskoka Memorial, Programme de dépistage du cancer du sein de l'Ontario | Bracebridge |
| Muskoka Family Works, Huntsville, Services de médiation et de counselling Muskoka Family Works Mediation and Counselling | Huntsville |
| Muskoka Lakes Museum, Musée de Muskoka Lakes | Muskoka Lakes Township |
| Muskoka Residential Centre, Centre résidentiel Muskoka | Severn |
| Muskoka Seniors Home Assistance, Muskoka Seniors | Huntsville |
| Muskoka Small Business Centre | Bracebridge |
| My Friend Beth Senior & Support Services, Collingwood, Services senior et support My Friend Beth | Collingwood |
| My Friend's House, Refuge pour victimes de violence familiale | Collingwood |
| My Pre Academy | Barrie |
| My Sister's Place, Inactif People in Transition (Alliston) Inc., My Sister's Place | New Tecumseth |