The Tail of Goku (悟空のシッポ Gokū no Shippo, lit. "Goku's Tail") is the fortieth chapter of the Dragon Ball manga.
The cover shows a picture of Goku in a fighting pose, with the World Martial Arts Tournament arena in the background. The cover is in color, with a red-brown-gray-black color palette.
The chapter opens with Goku still ensnared in Giran's Merry-Go-Round Gum. As Goku attempts to escape, Giran says that the gum will become stickier the more he struggles. Giran punches Goku's head, then picks him up to throw him. Goku demands that Giran fight fair and square. Giran hurls Goku out of the ring, much to the consternation of his friends. Goku calls for the Flying Nimbus, which comes to his rescue, taking him back to the tournament ring. Giran complains that Goku's use of the Nimbus breaks the rules. The announcer, after conferring with the head priest, decides that he will allow the Nimbus to be used this time only. Giran is undaunted, as Goku is still trapped in the gum. He winds up for a monster punch, but is stunned when he misses. He soon sees that Goku has dodged by using his tail, which conveniently grew back at that moment, to swing on Giran's own tail. Goku's friends are flabbergasted by the sudden occurrence. Giran amazedly declares that Goku cannot be human. Goku then bursts free from the gum, then checks out his strength by kicking a large hole in the arena wall, noting that he is now much stronger (due to the tail). Giran, terrified, holds up a white flag to concede the match. Bulma nervously wonders when the next full moon is.
- The Viz release of this chapter has a self-declared "pointless page" after the chapter's second page. It depicts Master Roshi being hit in the head with a baseball while watching an attractive woman in a bikini.