M
- Madeira, Louis Childs, Jr., Papers (UPT 50 M181)
- Madeira, Percy C., Jr., Papers (UPT 50 M181.1)
- Marks, William Dennis, Papers (UPT 50 M346)
- Martin, Harry Mathias, Papers (UPT 50 M381)
- Martin, William, Papers (UPT 50 M379)
- Mask and Wig Club Records (UPS 68.1)
- Massiah, Frederick and Edith L., Papers (UPT 50 M417)
- McClellan Family Papers (UPT 50 MCC623)
- McCollin, Edward G., Collection (UPT 50 MCC699)
- McCracken, Josiah C., Papers (UPT 50 MCC883)
- McDonald, Harl, Papers (UPT 50 MCD675)
- McDowell, Stewart A., Collection (UPT 50 M138)
- McKenzie, R. Tait (Robert Tait), Papers (UPT 50 MCK37)
- McNeil Center for Early American Studies Records (UPB 159)
- Medical Bicentennial, 1965, Collection (UPG 225)
- Medical Buildings' Dedications Collection (UPG 35.9)
- Medico-Chirurgical College and Hospital of Philadelphia Records (UPC 50.3)
- Memorabilia Collection (MEM)
- Metallurgical Engineering Records (UPD 9.9)
- Meter, Frank, Papers (UPT 50 M589)
- Meyer, Louis Joseph, Papers (UPT 50 M612)
- Meyerhof, Otto, Papers (UPT 50 M613)
- Meyerson, Martin, Papers (UPT 50 M613M)
- Miller, Karl Greenwood, Papers (UPT 50 M649)
- Miller, Thomas Grier, Papers (UPT 50 M651)
- Miscellaneous Special Events and Organizations Collection (UPG 102)
- Molloy, Ruth Branning, Collection (UPT 50 M726)
- Molstad, Melvin Carl, Papers (UPT 50 M728)
- Moore School of Engineering Office of the Vice-Dean Records (UPD 8.1)
- Moore School of Engineering. Correspondence (UPD 8.5)
- Moore School of Engineering. Faculty Minutes (UPD 8.2)
- Moore School of Engineering. Office of the Director Records (UPD 8.4)
- Moore School of Engineering. Student Records (UPD 8.7)
- Moore, Alfred Fitler, Family Papers (UPT 50 M821)
- Morgan State College-Penn Cooperative Project Records (UPB 151)
- Morris, Jean C., Papers (UPT 50 M876)
- Morris, Robert H., Dental Practice Records (UPT 50 M875)
- Morrow, Glenn Raymond, Papers (UPT 50 M883)
- Morton, Harry E., Papers (UPT 50 M889)
- Mossell, Nathan Francis, Papers (UPT 50 M913)
- Mudd Family Papers (UPT 50 M944)
- Munger, George, Papers (UPT 50 M963)
- Murphy, Maurice Klaus Michael, Papers (UPT 50 M978)
- Murray, Donald Shipley, Papers (UPT 50 M972)
- Musical Club Records (UPS 510)
- Muybridge, Eadweard, Collection (UPT 50 M993)