P
- Pacific (1900–1904)
- Pacific Special (1911–1913)
- Packard (1895–1898)
- Packard (1899–1958)
- Paco (1908–1909)
- Paige-Detroit (1908–1911; Paige 1911-1928; Graham-Paige 1928-1930)
- Page (1906–1908)
- Palmer (1905–1906)
- Palmer-Singer (1908–1914)
- Pan (1919–1921)
- Panam (1902–1903)
- Pan-American (1917–1922)
- Paragon (1906)
- Parenti (1920–1922)
- Parry (1910; New Parry 1911-1912)
- Parsons Electric (1905–1906)
- Partin (1913; Partin-Palmer 1913-1917)
- Paterson (1909–1923)
- Pathfinder (1912–1917)
- Patterson-Greenfield (1916–1919)
- Pawtucket (1901–1902)
- Payne-Modern (1907–1908)
- Peerless (1900–1933)
- Peerless Steam (1901)
- Pence (circa 1905)
- Peninsular (see Marquette)
- Penn (1901)
- Penn (1908)
- Penn (1910–1913)
- Pennant (1924–1925)
- Pennington (1894–1900)
- Pennsy (1916–1918)
- Pennsylvania (1907–1911)
- People's (1900–1902)
- Perfection (1907–1908)
- Perfex (1912–1913)
- Perrett Electric (1900)
- Peter Pan (1914–1915)
- Peters-Walton (1915; Peters Tricar 1916)
- Petrel (1909–1912)
- Phelps (1903–1905)
- Phianna (1917–1922)
- Phillips (1980-198?)
- Phipps-Grinnell (1911; Phipps Electric 1912)
- Pickard (1909–1912)
- Piedmont (1917–1922)
- Pierce-Arrow (1900–1938)
- Pierce-Racine (1904–1911)
- Piggins (1908–1910)
- Pilgrim (1911)
- Pilgrim (1913–1914)
- Pilgrim (1915–1918)
- Pilliod (1915–1916)
- Pilot (1909–1924)
- Pioneer (1907–1912)
- Pioneer (1914)
- Pittsburgh Six (1908–1911)
- Planche (see Roebling-Planche)
- Plass (1897)
- Playboy (1947–1951)
- Plymouth (1910)
- Plymouth (1928–2001)
- Pneumobile (1914–1915)
- Pomeroy (1902)
- Pomeroy (1920–1924)
- Ponder (see Bour-Davis)
- Pontiac (1907–1908)
- Pontiac (1926–2010)
- Pope-Hartford (1904–1914)
- Pope-Robinson (1903–1904)
- Pope-Toledo (1903–1909)
- Pope-Tribune (1904–1908)
- Pope-Waverley (1903–1908)
- Port Huron (see Havers)
- Porter (1900–1901)
- Porter (1919–1922)
- Portland (1914)
- Postal (1906–1908)
- Powell (1930s-1960s)
- Powell (1955–1956)
- Powercar (1909–1911)
- Pratt-Elkhart (1909–1911; Pratt 1911-1915)
- Premier (1902–1926)
- Premocar (1920–1923)
- Prescott (1901–1905)
- Primo (1910–1912)
- Princess (1914–1918)
- Prospect (1902, 1907–1908)
- Pullman (1905–1917)
- Pungs Finch (1904–1910)
- Puritan (1902–1905)
- Puritan (1913–1914)
Read more about this topic: List Of Defunct Automobile Manufacturers Of The United States