Atlantic Petroleum was an oil company in the Eastern United States headquartered in Philadelphia, Pennsylvania, and a direct descendant of the Standard Oil Trust. It was also one of the companies that merged with Richfield Oil Corporation to form the "AtlanticRichfield Co.", later known as ARCO.

After an unsuccessful spinoff from ARCO, Atlantic was acquired by Sunoco in 1988. The remainder of ARCO was later acquired by BP, but BP later sold most of Arco's retail assets and brand name to Tesoro, later briefly renamed to Andeavor, and eventually acquired by Marathon Petroleum, which owns the ARCO brand to this day.

Atlantic was founded as the "Atlantic Petroleum Storage Company" in 1866, in the then-fledgling oil business. In 1874, the company, now known as "Atlantic Refining", was purchased by John D. Rockefeller and integrated as part of Standard Oil. The acquisition gave Rockefeller a major presence on the East Coast in his growing empire.

In 1886, after acquiring many other oil companies, the Standard Oil Trust organized territories for their companies. Atlantic's territory covered the entire state of Delaware, the southern half of New Jersey, and the southeasternmost corner of Pennsylvania, essentially giving Atlantic the entire Philadelphia area.

Due to antitrust issues that would eventually lead to the demise of the Trust in 1911, Atlantic absorbed fellow Standards Acme Oil of Pennsylvania and Pittsburgh-based Standard Oil (of Pennsylvania) in 1892.

As a result of the Sherman Antitrust Act, the Standard Oil Trust was broken up, and Atlantic was one of 11 companies to acquire rights to the Standard name. (In all, 35 companies were formed from the breakup, the most notable ones without rights to the Standard name being the Ohio Oil Company, which became Marathon and South Penn Oil Company, which though various mergers and acquisitions became Pennzoil.) Atlantic's rights were in the entire states of Pennsylvania and Delaware, as it had given up the southern half of New Jersey to Jersey Standard (later Exxon, now ExxonMobil).

However, like fellow baby Standard Conoco (now ConocoPhillips), Atlantic found more marketing power in its own name than the Standard name (a rarity at the time), and declined the option to use the name. The rights to the Standard name in Pennsylvania would be acquired by a newly formed Standard Oil of Pennsylvania, which would be acquired by Exxon in the late 1930s. ExxonMobil still owns the rights to the Standard name in Pennsylvania and Delaware.

Over the years, Atlantic would expand up across the East Coast of the U.S., mainly through acquisitions.