Alexander Calder (Lawnton, Pennsylvania, 1898 – New York, New York, 1976) is best known for his delicate abstract sculptures, known as mobiles, which introduced motion into a formerly static medium and revolutionized twentieth-century sculpture.

Born into a family of artists, Calder first earned a degree in mechanical engineering before studying at the Art Students League in New York. Moving to Paris in 1926, he began "drawing" in wire three-dimensionally, producing portrait heads of celebrities and friends, and channeled his lifelong fascination with the circus into Cirque Calder, a miniature performance of wire and found materials he staged by hand for the Parisian avant-garde. "I think best in wire," he later said. After visiting Piet Mondrian's studio in 1930, Calder was inspired by nonobjective and geometric art, and in 1931 he created his first mobile, a term coined by Marcel Duchamp as a French pun on words meaning both "motion" and "motive."