The Phosphorescent Rat is the fourth album by the blues rock group Hot Tuna, released in early 1974 as Grunt BFL1-0348. This was the first Hot Tuna album recorded after guitarist Jorma Kaukonen and bass player Jack Casady had left Jefferson Airplane. They were joined as before by drummer Sammy Piazza, though Papa John Creach had left the band for Jefferson Starship. The band's playing was moving away from the softer, more acoustic sound of their first three albums, and towards a hard rock sound that would be explored on their next three albums.