Asian American and Pacific Islander Heritage Month—also known as Asian Heritage Month in Canada—is celebrated in May each year to honor the achievements of Asian and Pacific Islander Americans and Canadians in medicine, education, politics, entertainment, sports, and many other important fields. 

The month of May was chosen in the U.S. to commemorate the arrival of the first Japanese immigrants to the United States in May of 1843 and the completion of the First Transcontinental Railroad (an effort largely fueled by Chinese immigrants) in May, 1869.

AAPI Heritage Month grew out of the Asian/Pacific American Heritage Week that Congress established in 1978. President Jimmy Carter signed the proclamation that year, and the first observance was held in 1979.

Originally, the resolution did not establish Asian/Pacific American Heritage Week as an annual event. Instead, the president had to issue a proclamation each year declaring the commemorative week. In 1990 President George H.W. Bush expanded the observation into a full month, and it was called Asian/Pacific American Heritage Month. In 1992 he permanently designated the month of May as an annual observance. President Barack Obama noted the contributions of Pacific Islanders and changed the name to Asian American and Pacific Islander Heritage Month, in 2009.