Mother's Day is a celebration honoring mothers and celebrating motherhood, maternal bonds and the influence of mothers in society. It is celebrated on various days in many parts of the world, yet most commonly in March, April, or May. It complements Father's Day, the celebration honoring fathers.

Celebrations of mothers and motherhood occur throughout the world; many of these can be traced back to ancient festivals, like the Greek cult to Cybele or the Roman festival of Hilaria. The modern US holiday is not directly related to these.

Florence Owens Thompson (September 1, 1903 – September 16, 1983), born Florence Leona Christie, was the subject of Dorothea Lange's photo Migrant Mother (1936), an iconic image of the Great Depression. The Library of Congress entitled the Migrant Mother image, "Destitute pea pickers in California. Mother of seven children. Age thirty-two. Nipomo, California."