The Opium Advisory Committee (OAC), more formally entitled the Advisory Committee on the Traffic in Opium and other Dangerous Drugs, was a body of the League of Nations as according to the Organization of the League of Nations being responsible for international cooperation in the areas related to opium, narcotic drugs and those other drugs classified as "dangerous."

The first meeting of the OAC lasted for 3 days, from the 2nd to the 5th of May, 1921.

The founding members of the Committee consisted of the following:

The main differences in the approaches to opium control and enforcement among the delegations stemmed from the fact that in North America, there was a well established Temperance movement, whereas the European colonial powers were making millions in their opium monopolies.

In the United States, the Harrison Narcotics Tax Act was passed in 1918, effectively banning opium outright without a medical license to supply its derivatives as painkillers. For several years, the United States maintained narcotics control through its Miscellaneous Division, but the Narcotics Division of the Bureau of Prohibition was established in the same year of 1920 as the League of Nations. In the following decade, Narcotics Agents would make more arrests overall than their Dry Agent counterparts. Also in 1920, the Canadians had passed the Opium and Narcotic Drug Act. Shortly afterward, in 1921, the Canadian Narcotics Division was established under the ownership of the Royal Canadian Mounted Police and the Minister of Health.

Meanwhile, the three main European delegations had by this point effectively monopolized the drug trade in their Asian colonies. The British were committed to a policy of Opium farming in their colonial possessions at this point, and the French managed an Opium Regie in their colony of French Indochina. However, by far the most successful colonial monopoly over opium and its derivatives was the Netherlands' Opiumregie, which held a vice-grip over the colony of the Dutch East Indies, being modeled as it were after several successive state monopolies on opium that the Dutch had held in these islands since the early 1700's.

Another point of contention was the fear that the European colonial powers held over the rise of communism in Asia, and specifically in China. Where the Japanese and Chinese ministers had been old friends, and would often support one another's decisions – John Chambers, the delegate representing India, had previously laid heavy claims at the International Opium Convention that the majority of opium coming into his country was being produced in India.

When the League of Nations was created in 1920, a schism formed within the leadership as to the approach of global enforcement – those who were, as the saying goes, "tough on crime," felt that the mechanisms outlined in the framework of the OAC were not strong enough to effectuate adequate drug controls. Since the Congress of the United States had not at this point ratified its membership in the League, the US Commissioner for Narcotics at the time, Levi G. Nutt, was not able to fully influence global policy to reflect his hard domestic sentencing for addicts. He did, however, find an ally in Elizabeth Wright, who served as the first American Assessor of the OAC, and was the widow of the former United States Opium Commissioner. Other allies of the former Commissioner, including Charles Brent, took the opportunity to speak ad naseum on the American view.