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; the group had been waiting for their return all through 1973 and when this didn't happen, the remaining members changed the name to Jefferson Starship at the start of 1974. The two core members were joined as before by drummer Sammy Piazza, though Papa John Creach had left the band, instead staying on with 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.