| IENA | Lodi (I) | 1922 – 1925 | | |
| IFA | Zwickau (D) | 1949 – 1956 | | |
| IMP | Glendale (USA) | 1949 – 1950 | | |
| Imperia | Lüttich/Nessonvaux (B) | 1906 – 1948 | | |
| Imperial | USA | >1955 | | |
| Infinity | Japan / USA | | | |
| International | Chicago (USA) | 1907 – 1911 | | |
| International | (GB) | 1898 – 1904 | | |
| Innocenti | Mailand (I) | 1960 - | | |
| Invicta | Turin (I) | 1903 – 1906 | | |
| Invicta | Cobham/Chelsea (GB) | 1924 – 1950 | | |
| Iris | Willesden (GB) | 1905 – 1915 | | |
| ISO (Isetta) | Mailand (I) | 1953 – 1976 | | |
| Isotta-Fraschini | Mailand (I) | 1900 – 1949 | | |
| Itala | Turin (I) | 1904 – 1933 | | |
| Italia | Bologna (I) | 1907 – 1908 | | |
| Italsuisse | Genf-Carouge (CH) | 1960 – 1967 | | |
| Jackson | (GB) | 1899 – 1914 | | |
| Jackson | (USA) | 1903 – 1923 | | |
| Jaguar | Coventry (GB) | 1945 - | | |
| Jawa | (CSSR) | 1934 - 1939 | | |
| Jehle | Schaan (FL) | 1976 - | | |
| Jenatzy (Jamais Contente) | Belgien | 1899 | | |
| Jensen | West Bromwich (GB) | 1936 – 1976 | | |
| Jordan | Cleveland (USA) | 1916 – 1931 | | |
| Joswin | Berlin (D) | 1920 – 1926 | | |
| Jowett | Idle Bradford (GB) | 1905 – 1954 | | |
| Junior | Turin (I) | 1905 – 1909 | | |
| Kaiser | Willow Run (USA) | 1946 – 1955 | | |
| Kämper | Berlin (D) | 1905 – 1906 | | |
| Keeton | (USA) | | | |
| Kellison | (USA) | 1955 - 1972 | | |
| Kenter | (D) | | | |
| King | Detroit/Buffalo (USA) | 1910 – 1924 | | |
| King Midget | Athens (USA) | 1946 – 1970 | | |
| Kissel | Hartford (USA) | 1906 – 1931 | | |
| Kleinschnittger | Arnsberg (D) | 1950 – 1954 | | |
| Knight | Farnham (E) | 1895 | | |
| Komet | (D) | | | |
| Komnick | Elbingen (D) | 1907 – 1927 | | |
| Köng | Basel (CH) | 1935 - | | |
| Körting | (D) | | | |
| Kriéger | (F) | 1897 – 1909 | | |
| Kroboth | (D) | | | |
| Kurtis | Los Angeles/Glendale (USA) | 1949 – 1950 | | |
| K-Wagen (Wunibald Kamm) | (D) | 1938/39 | | |
| Lafayette | (USA) | 1920 – 1949 | | |
| Lafitte | Paris (F) | 1923 – 1928 | | |
| La France (American La France) | New York (USA) | 1921 – 1931 | | |
| Lagonda | Staines/Feltham/NewportPagnell (GB) | 1905 - | | |
| Lambert | Macon/Reims/Giromagny (F) | 1926 – 1954 | | |
| Lambert | 4 weitere Firmen in USA, GB und F | | | |
| Lamborghini | Sant’Agata Bolognese (I) | 1963 - | | |
| Lammas Graham | (GB) | 1936 – 1938 | | |
| Lanchester | Coventry (GB) | 1895 – 1956 | | |
| Lancia | Turin (I) | 1906 - | | zur Bildergalerie |
| Langenthal | Langenthal (CH) | 1888 - | | |
| Lanza | Turin (I) | 1898 – 1903 | | |
| Lasalle ( La Salle) | Detroit (USA) | 1927 – 1949 | | |
| Laurin & Klement | Mlada Boleslav (CSSR) | 1906 – 1928 | | |
| Lea-Francis | Coventry (GB) | 1904 - | | |
| Lentz | Mailand (I) | 1906 – 1908 | | |
| Léon-Bollée | | | | |
| Leone | Turin (I) | 1949 – 1950 | | |
| Leon-Laisne | Lille/Nantes (F) | 1920 – 1937 | | |
| Ley (Loreley) | Arnstadt (D) | 1905 – 1927 | | |
| Leyat | Meursault/Paris (F) | 1913 – 1927 | | |
| Leyland | Leyland (GB) | 1920 – 1923 | | |
| Liberty | (USA) | 1976 | | |
| Licorne (La) | (F) | 1907 – 1939 | | |
| Liliput | Gaggenau (D) | 1905 | | |
| Lincoln | Detroit (USA) | 1920 - | | |
| Lindcar | (D) | | | |
| Lion-Peugeot | Beaulieur-Valentigney (F) | 1897 – 1910 | | |
| Lloyd | (D) | 1950 – 1957 | | |
| Locomobile | Bridgeport (USA) | 1899 – 1929 | | |
| Lohner-Porsche | (AUT) Wien | | | |
| Lorraine-Dietrich | Lunéville/Niederbronn/Argenteuil (F/D) | 1897 – 1935 | | |
| Lotus | Hornsey/Cheshunt/Hethel (GB) | 1952 - | | |
| Lozier | Plattsburg/Detroit (USA) | 1905 – 1917 | | |
| Luc Court | Lyon (F) | 1899 – 1936 | | |
| Lutzmann | Dresden (D) | 1897 – 1898 | | |
| Luwo | (D) | | | |
| Lux | Turin (I) | 1906 – 1907 | | |
