| M.I.G. Group of Health Services | Other Public Sector Employers | 2000 | 1 | $118,463 |
| Maamwesying North Shore Community Health Services | Other Public Sector Employers | 2025 | 12 | $154,452 |
| Maamweysing North Shore Community Health Services Incorporated | Other Public Sector Employers | 2016 | 2 | $129,767 |
| Macaulay Child Development Centre | Other Public Sector Employers | 2017 | 3 | $131,168 |
| MacKay Manor Inc | Other Public Sector Employers | 2025 | 2 | $151,579 |
| MacKenzie Health | Hospitals & Boards of Public Health | 2025 | 1,311 | $127,412 |
| Madame Vanier Children's Services | Other Public Sector Employers | 2025 | 4 | $139,274 |
| Madawaska Valley Association for Community Living | Other Public Sector Employers | 2025 | 1 | $111,198 |
| Madawaska Valley Family Health Team | Other Public Sector Employers | 2021 | 2 | $113,924 |
| Madison Community Services | Other Public Sector Employers | 2025 | 1 | $162,624 |
| Magellan Community Care | Other Public Sector Employers | 2025 | 1 | $103,237 |
| Mainstay Housing | Other Public Sector Employers | 2020 | 2 | $125,072 |
| Mainstream Services | Other Public Sector Employers | 2025 | 3 | $123,206 |
| Maison Baldwin House | Other Public Sector Employers | 2025 | 1 | $109,067 |
| Maison d'Amitie | Other Public Sector Employers | 2025 | 1 | $113,072 |
| Maison d'Amitie / Maison d'Amitie | Other Public Sector Employers | 2023 | 1 | $115,000 |
| Maison de Soins Palliatifs de Sudbury Hospice | Other Public Sector Employers | 2025 | 7 | $116,478 |
| Maison d’Hebergement Pour Femmes Francophones | Other Public Sector Employers | 2022 | 1 | $102,627 |
| Maison Fraternite | Other Public Sector Employers | 2012 | 1 | $126,706 |
| Maison Fraternite – Fraternity House | Other Public Sector Employers | 2020 | 1 | $110,704 |
| Maison Interlude House Inc | Other Public Sector Employers | 2025 | 1 | $112,302 |
| Maison Interlude House Inc / Maison Interlude House Inc | Other Public Sector Employers | 2023 | 1 | $103,385 |
| Maison Vale Hospice | Other Public Sector Employers | 2015 | 1 | $110,238 |
| Maitland Valley Family Health Team | Other Public Sector Employers | 2023 | 2 | $122,279 |
| Maltby Centre | Other Public Sector Employers | 2025 | 12 | $123,907 |
| Malton Neighbourhood Services | Other Public Sector Employers | 2023 | 2 | $127,917 |
| Malvern Family Resource Centre | Other Public Sector Employers | 2025 | 2 | $104,614 |
| Mamaweschen N.Shore Tribal Cncl | Other Public Sector Employers | 1999 | 1 | $117,000 |
| Mamaweswen North Shore Tribal Council | Other Public Sector Employers | 2003 | 1 | $130,000 |
| Mamaweswen Nrth Shore Tribal Co. | Other Public Sector Employers | 2002 | 1 | $130,000 |
| Mamaweswen, the North Shore Tribal Council | Other Public Sector Employers | 2012 | 1 | $146,831 |
| Mamaweswen, the North Shore Tribal Council Secretariat | Other Public Sector Employers | 2025 | 2 | $101,793 |
| Management Board Secretariat | Government of Ontario – Ministries | 2004 | 96 | $118,844 |
| Mango Tree Family Health Team | Other Public Sector Employers | 2022 | 1 | $134,239 |
| Manitoulin Central Family Health Team | Other Public Sector Employers | 2023 | 1 | $104,781 |
| Manitoulin Family Resources Inc | Other Public Sector Employers | 2025 | 2 | $126,765 |
| Manitoulin Health Centre | Hospitals & Boards of Public Health | 2025 | 49 | $127,929 |
| Manitoulin Sudbury District SSAB | Other Public Sector Employers | 2005 | 1 | $119,677 |
| Manitoulin-Sudbury CCAC | Other Public Sector Employers | 1999 | 1 | $104,476 |
| Manitoulin-Sudbury Dist Soc Srvcs AdmBd | Municipalities & Services | 2004 | 1 | $110,499 |
| Manitoulin-Sudbury District Services Board | Other Public Sector Employers | 2025 | 91 | $120,648 |
| Manitoulin-Sudbury District Social Srvcs. Admin. Board | Other Public Sector Employers | 2009 | 1 | $100,812 |
| Manitoulin-Sudbury DSSAB | Municipalities & Services | 2005 | 1 | $119,677 |
| Manitouwadge General Hosp. | Hospitals & Boards of Public Health | 2004 | 1 | $123,607 |
| Manitouwadge General Hospital | Hospitals & Boards of Public Health | 2018 | 7 | $103,800 |
| Manitowaning Medical Clinc Board | Other Public Sector Employers | 2023 | 2 | $111,265 |
| Manufacturing Research Corporation of Ontario | Other Public Sector Employers | 1996 | 1 | $100,000 |
| Maple Family Health Team Inc | Other Public Sector Employers | 2023 | 6 | $122,361 |
| Marathon Family Health Team | Other Public Sector Employers | 2023 | 1 | $108,081 |
| March of Dimes Canada | Other Public Sector Employers | 2025 | 63 | $143,575 |
| Margaret Fraser House | Other Public Sector Employers | 2023 | 1 | $145,000 |
| Margaret's Housing and Community Support Services Inc. | Other Public Sector Employers | 2025 | 1 | $144,999 |
| Marianhill | Other Public Sector Employers | 2004 | 1 | $106,051 |
| Marianhill Inc | Other Public Sector Employers | 2025 | 9 | $133,652 |
| Mariann Home | Other Public Sector Employers | 2015 | 1 | $114,976 |
| Mariann Nursing Home and Residence | Other Public Sector Employers | 2025 | 2 | $132,915 |
| Markham Family Health Team | Other Public Sector Employers | 2023 | 5 | $118,281 |
| Markhaven Inc. | Other Public Sector Employers | 2015 | 1 | $120,091 |
| Markhaven Incorporated | Other Public Sector Employers | 2025 | 6 | $123,966 |
| MaRS | Other Public Sector Employers | 2005 | 3 | $179,167 |
| MaRS Discovery District | Other Public Sector Employers | 2025 | 42 | $150,022 |
| MaRS Innovation | Other Public Sector Employers | 2017 | 9 | $209,237 |
| Mars Investment Accelerator Fund Inc | Other Public Sector Employers | 2018 | 7 | $187,656 |
| Marten Falls First Nation | Other Public Sector Employers | 2025 | 9 | $123,148 |
| Mary Bergland CHC | Other Public Sector Employers | 2001 | 2 | $119,535 |
| Mary Berglund Community Health Centre | Other Public Sector Employers | 2016 | 1 | $113,958 |
| Mary Berglund Community Health Centre Hub | Other Public Sector Employers | 2025 | 2 | $130,338 |
| Mary Berglund Community Hlth Ctr | Other Public Sector Employers | 2000 | 1 | $150,382 |
| Mary Berglund Community Hth Ctr. | Other Public Sector Employers | 1999 | 1 | $136,983 |
| Mary Centre | Other Public Sector Employers | 2025 | 1 | $181,387 |
| Mary Centre of the Archdiocese of Toronto | Other Public Sector Employers | 2023 | 1 | $162,268 |
| Mary Centre of the Archdioses of Toronto | Other Public Sector Employers | 2006 | 1 | $109,833 |
| Marycrest Home for the Aged | Other Public Sector Employers | 2008 | 1 | $114,230 |
| Maryvale | Other Public Sector Employers | 2025 | 4 | $133,645 |
| Maryvale Adolescent & Family Services | Other Public Sector Employers | 2008 | 2 | $298,112 |
| Massey Centre for Woman | Other Public Sector Employers | 2015 | 1 | $115,000 |
| Massey Centre for Women | Other Public Sector Employers | 2022 | 2 | $121,579 |
| Matawa First Nations Management | Other Public Sector Employers | 2025 | 33 | $128,880 |
| Matawa Health Co-operative Inc | Other Public Sector Employers | 2025 | 7 | $201,267 |
| Materials and Manufacturing Ontario | Other Public Sector Employers | 2003 | 5 | $117,896 |
| Mathematics of Information Technology & Complex Systems Inc. | Other Public Sector Employers | 2013 | 1 | $114,533 |
| Mathematics of Information Technology and Complex Systems (MITACS) Inc | Other Public Sector Employers | 2025 | 40 | $132,132 |
| Mathematics of Information Technology and Complex Systems Inc. | Other Public Sector Employers | 2014 | 2 | $147,343 |
| Matheson / Iroquois Falls / Cochrane Group of Health Services | Hospitals & Boards of Public Health | 2025 | 57 | $131,459 |
| Mattagami First Nation | Other Public Sector Employers | 2024 | 1 | $109,795 |
| Mattawa General | Hospitals & Boards of Public Health | 2003 | 1 | $135,989 |
| Mattawa General Hospital Inc | Hospitals & Boards of Public Health | 2006 | 2 | $122,751 |
| Matthew House Refugee Services (Ottawa) Inc. | Other Public Sector Employers | 2023 | 1 | $100,000 |
| Max Ottawa Community Health | Other Public Sector Employers | 2025 | 1 | $105,962 |
| Maxville Manor | Other Public Sector Employers | 2025 | 7 | $113,355 |
| Maytree Foundation | Other Public Sector Employers | 2011 | 1 | $158,386 |
| McCausland Hospital | Hospitals & Boards of Public Health | 2015 | 5 | $111,483 |
| McCormick Care Group | Other Public Sector Employers | 2025 | 10 | $126,326 |
| McMaster Divinity College | Universities | 2024 | 5 | $148,713 |
| McMaster University | Universities | 2025 | 1,966 | $165,955 |
| McMichael Canadian Art Collection | Crown Agencies | 2025 | 6 | $132,717 |
| Meals on Wheels (Ottawa) | Other Public Sector Employers | 2025 | 1 | $168,317 |
| Medecins Sans Frontieres/Doctors Without Borders(Msf Canada) | Other Public Sector Employers | 2017 | 4 | $117,789 |
| Mediaedge Communications Inc | Other Public Sector Employers | 2022 | 1 | $196,445 |
| Mediasmarts Habilomédias | Other Public Sector Employers | 2025 | 2 | $138,842 |