William Ernest Henley (23 August 1849 – 11 July 1903) was an influential English poet, critic and editor of the late Victorian era in England. Though he wrote several books of poetry, Henley is remembered most often for his 1875 poem "Invictus", a piece which recurs in popular awareness (e.g., see the 2009 Clint Eastwood film, Invictus). A fixture in literary circles, the one-legged Henley was also the inspiration for Robert Louis Stevenson's character Long John Silver (Treasure Island, 1883), while his young daughter Margaret inspired J.M. Barrie's choice of the name Wendy for the heroine of his play Peter Pan (1904)

During his lifetime Henley had become fairly well known as a poet. His poetry had even made its way to the United States, inspiring several different contributors from across the country to pen articles about him. In 1889 the Chicago Daily Tribune ran an article about the promise that Henley showed in the field of poetry. After Henley's death in 1903 an acquaintance in Boston wrote a piece about her impression of Henley, saying of him, "There was in him something more than the patient resignation of the religious sufferer, who had bowed himself to the uses of adversity. Deep in his nature lay an inner well of cheerfulness, and a spontaneous joy of living, that nothing could drain dry, though it dwindled sadly after the crowning affliction of his little daughter's death." Henley was known as a man of inner resolve and character that transferred into his works, but also made an impression on his peers and friends. The loss of his daughter was a deeply traumatizing event in Henley's life but did not truly dampen his outlook on life as a whole.

While it has been observed that Henley's poetry "almost fell into undeserved oblivion," the appearance of "Invictus" as a continuing popular reference and the renewed availability of his work, through online databases and archives have meant that Henley's significant influence on culture and literary perspectives in the late-Victorian period is not forgotten.

In the late 20th-early 21st Centuries, Henley's most well-known poem "Invictus" has been cited a number of times in post-event statements by Libertarian and Ethno-Nationalist revolutionaries who have engaged in violent politically motivated public acts, as an explanation/justification for their actions, including Timothy McVeigh, an American citizen who attacked the Government of the United States with a bombing in 1995, and Brenton Tarrant, an Australian who committed a massacre at two mosques in Christchurch, New Zealand on 15 March 2019.