This is the pathway a character has to travel along to get to their ultimate goal. Deviating from the path is not an option, and even if you attempt to do so for any brief period or for any reason, inevitably you'll have to go back onto the path to complete the journey's chief objective.
It doesn't have to be a literal pathway, but can refer mainly to the route that a character needs to travel along to get from start to finish. Also note that there aren't multiple goals to be fulfilled beyond the end of the journey; the journey's end is just that.
Not related to No Sidepaths, No Exploration, No Freedom, which focuses mainly on videogames' design; this trope focuses on linear storylines within all media.
If the ultimate goal of the story is to get the character home, that's The Homeward Journey. If the destination is a place of legend, that's The Promised Land. If this is the only way to get to the villain's lair, it's Walk into Mordor.
- The Snake Way in Dragon Ball Z could be seen as this. Goku had to travel along this path to get back to Earth from the afterlife in time to fight the Saiyans.
- A variation of this takes place in One Piece: the ultimate goal for all pirates searching for the titular treasure is Raftel, the last island in the Grand Line, where Gold Roger is believed to have hidden the treasure. Each pirate crew's navigator has a Log Pose (a compass worn on the wrist like a watch) that points out the direction to the next island along the journey...but it's a variation because there are several winding paths along the Grand Line beginning from Reverse Mountain, all of which have in common Raftel as the final stop. Therefore, the specific pathway that the Straw Hats have been traveling from Reverse Mountain is just one of several routes they could have sailed.
- In both Jumanji and Zathura, once the protagonists have started playing the eponymous games, they must play the game all the way through in order to escape and undo the damage done.
- Labyrinth: Although she is of course running around (and often getting lost) in a deadly maze, Sarah has only one goal: to find Toby in the center of the labyrinth and every step she takes is to try to get her further towards that goal.
- The Trope Namer comes from The Wonderful Wizard of Oz, and led the protagonists to the Emerald City, as the page image shows.
- John Bunyan's The Pilgrim's Progress. Stick to the straight and narrow, or you will regret it. Even leaving it for an easier road that parallels it is bad, as Christian is quick to find out.
- C.S. Lewis's The Pilgrim's Regress has the same basic theme, except most of the book consists of deviations from the path, with the justification that the protagonist can only clearly see the part already traveled. Once finally accepting divine guidance and correction, the remainder of the path is clear and easily traversed. Whether the added parts of the journey were worth it in the end is ambiguous.
- The Mississippi River functions as this in The Adventures of Huckleberry Finn. At first, they were floating down to reach Cairo, Illinois, from whence they could sell the raft and buy tickets up the Ohio into the free states, but after they miss Cairo in a fog, they keep heading south...kinda just because.
- Literally Zig-Zagged on Star Trek: Voyager with Voyager going back and forth from toeing the straight line to the Alpha Quadrant, completing minor story arcs and plain old Monster of the Week detours.
- In Pushing Daisies S 1 E 7 The Smell Of Success, the team goes into the sewers to follow a "yellow thick hose".
- Played straight in Milton Bradley's Game of Life. There is only one end goal but the path there can branch or double back again.
- BioShock 2: Maps of the Atlantic Express essentially plot out the entire game.
- Lemmings 3D has a level called "Follow The Yellow Brick Road", where you have to do just that (it's a bit harder than it sounds).
- The Stanley Parable: At one point the narrator gets so frustrated with the player's refusal to play the game in his way that he creates "The Stanley Parable Adventure Line" which is simply a thick yellow line which the player must follow.
- Slave.In.Utero's Tower of God knows only one way. Up, from testing area to testing area.
- The Hanna-Barbera Alice in Wonderland has Alice following the Unwinding Road, which unscrolls before her like a carpet (not yellow, though).