The name became regularly used in the Christian world due to the fame of Saint Anthony the Great, a 4th-century Egyptian hermit who founded Christian monasticism. Its popularity was reinforced in the Middle Ages by the 13th-century Saint Anthony of Padua, the patron saint of Portugal. It has been commonly (but incorrectly) associated with Greek ἄνθος (anthos) meaning "flower", which resulted in the addition of the h to this spelling in the 17th century.
A famous bearer was the Italian Renaissance painter Antonio Pisanello (c. 1395-1455). It is also the name of the main character in The Merchant of Venice (1596) by William Shakespeare.
Apart from royalty, this name was only moderately popular in France during the Middle Ages. After the French Revolution, when Louis XVI was guillotined, it became less common.
The Normans brought the name to England, where it was usually spelled Lewis, though the spelling Louis has been more common in America. Famous bearers include French scientist Louis Pasteur (1822-1895), Métis leader Louis Riel (1844-1885), who led a rebellion against Canada, Scottish author Robert Louis Stevenson (1850-1894), who wrote Treasure Island and Dr Jekyll and Mr Hyde, and American jazz musician Louis Armstrong (1901-1971).
Before 1980, this was an uncommon masculine name in America. During the 1980s and 90s this name steadily increased in popularity for both boys and girls, and from 2003 onwards it has been more common for girls in the United States. Elsewhere in the English-speaking world, such as the United Kingdom and Australia, it has remained largely masculine.