The Chronicles of Riddick films don't mention galaxies but the novelizations contradict each other. The novelization to Pitch Black by Frank Lauria implies that humans have colonised several galaxies. It says that Riddick worked in the Sigma Galaxy and that Johns chased him across 3 galaxies. But the novelisation to The Chronicles of Riddick by Alan Dean Foster implies that everything takes place within one galaxy.
Star Wars, of course, takes place solely in A Galaxy Far, Far Away, with no explanation whatsoever. The Empire rules over the whole galaxy, hyperspace travel can launch even small Space Fighters halfway across the galaxy in days or hours, and the Rebel fleet hides above the galactic plane at the end of The Empire Strikes Back (nicely averting 2-D Space in the process), but intergalactic travel isn't even mentioned.
In Star Trek: The Original Series, when traveling across the galaxy seemed to take just a few days or weeks, they had the "Galactic Barrier", a mysterious energy field blocking intergalactic travel. There is at least one speciesnote that comes from Andromeda, but takes 300 years or so to send a ship across the void, and the Planet Killer of episode "The Doomsday Machine" was believed to be extra-galactic in origin. Later series dropped the idea of the Galactic Barrier and changed warp speed to Traveling at the Speed of Plot.
The Hitchhiker's Guide to the Galaxy is apparently set entirely within The Milkyway Galaxy. Despite all the various forms of faster-than-light travel, extradimensional beings, and travel driven by improbability. There is one point in the story where the cast are escaping from Milliways and find themselves headed into intergalactic space — promptly running for the escape pods. Mind, there were other reasons not to want to be aboard that ship at that particular time. Although, when the characters are searching for the real power behind the galactic throne, someone says "maybe he rules the whole universe" and this is thenceforth assumed to be true.