The Magnolia Petroleum Company was an early twentieth century petroleum company in Texas founded on April 24, 1911 by the Sealy family of Galveston, as a consolidation of several earlier companies. Standard Oil of New York (Socony) exchanged its stock for all of the Magnolia stock (except seven shares for the Directors) in December 1925 though it continued to operate as an affiliate of Socony. Socony merged with Vacuum Oil Company in 1931, becoming Socony-Vacuum Oil Company. Magnolia Petroleum continued to operate as a subsidiary of Socony-Vacuum. In 1959, Magnolia was fully incorporated into the Mobil division of Socony-Vacuum, which later changed its name to Socony Mobil and, ultimately to Mobil Oil Corporation.
The emblem of Magnolia Petroleum Company was originally a magnolia blossom (note the logo in the accompanying photo). When Socony merged with Vacuum in 1931, Socony-Vacuum as well as Magnolia began using Vacuum's red Pegasus logo, as well as the Mobil name for its products (Mobilgas, Mobiloil, etc.).
An unrelated Oklahoma-based company of the same name has been operating since 2008.