Neil is the English form of the Irish Niall, a name of uncertain meaning, usually explained as "champion" or "cloud"; Niall of the Nine Hostages was a legendary Irish king whose descendants include the O'Neills. Astronaut Neil Armstrong, the first man on the moon, and singers Neil Diamond and Neil Young made it an American classic of the 20th century. Neil was number 495 in 2000 and ranks number 851 among boys in 2025.