The Hull note, officially the Outline of Proposed Basis for Agreement Between the United States and Japan, was the final proposal delivered to the Empire of Japan by the United States before the attack on Pearl Harbor (December 7, 1941) and the Japanese declaration of war (seven and a half hours after the attack began). The note, delivered on November 26, 1941, is named for Secretary of State Cordell Hull (in office: 1933–1944). It was the diplomatic culmination of a series of events leading to the attack on Pearl Harbor. Notably, its text repeats previous American demands for Japan to withdraw from China and from French Indochina. No further American proposals were made before the attack on Pearl Harbor, as the US government had received intelligence that Japan was preparing an invasion of Thailand.

The United States objected to the Second Sino-Japanese War and the occupation of the Manchuria area of China by Japanese troops and settlers. In protest, the United States sent support to the Nationalist government of Chiang Kai-shek, starting with the Lend-Lease Act. In July 1941, Japanese military units occupied southern French Indochina, violating a gentlemen's agreement. Japanese bombers quickly moved into bases in Saigon and Cambodia, from which they could attack British Malaya. As a result, the US government imposed trade sanctions on Japan, including the freezing of Japanese assets in the United States; this effectively created an embargo of oil exports, as Japan did not have the necessary currency with which to buy American oil.

Dean Acheson, a senior US State Department official, was the key decision maker. He shifted American policy away from export restrictions and toward "full-blooded financial warfare against Japan". This financial freeze was described by Miller as "the most devastating American action against Japan".

On November 5, 1941, Emperor Hirohito approved, in Imperial Conference, the plan for the attack on Pearl Harbor. At the same time, his government made a last effort to arrive at a diplomatic solution of their differences with the United States. Ambassador Kichisaburō Nomura presented two proposals to the American government.

The first, Proposal A, was presented by him on November 6, 1941. It proposed making a final settlement of the Sino-Japanese War with a partial withdrawal of Japanese troops. United States military intelligence had deciphered some of Japan's diplomatic codes so they knew that there was a second proposal in case it failed. The United States government stalled and then rejected it on November 14, 1941.

On November 20, 1941, Nomura presented Proposal B, which offered to withdraw Japanese forces from southern Indochina if the United States agreed to end aid to the Nationalist Chinese, freeze military deployments in Southeast Asia (except for Japan's reinforcement of northern Indochina), provide Japan with "a required quantity of oil", and assist Japan in acquiring materials from the Dutch East Indies. The United States was about to make a counteroffer to this plan, which included a monthly supply of fuel for civilian use. However, President Franklin D. Roosevelt received a leak of Japan's war plan and news that Japanese troopships were on their way to Indochina. He then decided that the Japanese were not being sincere in their negotiations and instructed Secretary Hull to drop the counterproposal.^{[better source needed]}

By November 26, top American officials at the White House, State, Navy, and War Departments believed that Japan was moving invasion forces toward Thailand. They also believed that the Japanese foreign ministry had put an absolute deadline on negotiations of November 29 because "after that things are automatically going to happen". The Americans were convinced that war would start in a matter of days, probably with a surprise Japanese attack.

The previous plan, to present Japan with a temporary modus vivendi, was strongly opposed by China and Britain and dropped.