No. 4

No. 4 may refer to:


 * The number 4
 * No. 4, a 1966 experimental film directed by Yoko Ono
 * No. 4 (album), by the rock band Stone Temple Pilots
 * No. 4 Commando, Commando regiment in the UK Army
 * No. 4 Squadron RAAF, Royal Australian Air Force squadron
 * No. 4 Squadron RAF, Royal Air Force squadron
 * String Quartet No. 4 (disambiguation), the title of compositions by multiple composers
 * Symphony No. 4 (disambiguation), the title of compositions by multiple composers