I'm going to jump in and say that there's stuff that dwarfs most of the above.
The Ringworld from Larry Niven's ringworld gets a hyperdrive at one point, and there's the Puppeteer fleet of worlds, they literally got their star system moving. The comic Gold Digger has an artificial planet-ship.
The Culture has multiple ships in the 200km range, as their civilization is space-based so their 'cities/states' are often ships.
Dahak from David Weber's "Heirs of the Empire" series is literally Earth's Moon, and the 5th Imperium uses Planetoids as it's main warships too (under the idea that as long as one lives, it can re-create the Imperium).
Prince of Heroes has ships 'merely' in the 20 mile range for it's big ones, but fleet sizes in the billions exist, and there is a foe who's total strength is in the hundreds of billions/maybe a trillion range.
Schlock Mercenary has effectively an 'engine' on the entire galaxy.
And of course, it's not exactly a star ship, but there's the Xeelee Ring from Stephen Baxter's Xeelee sequence. It is an artificial construct that makes up a significant amount of the mass of the universe, made of woven galaxies and spun at incredible speed. Their enemies try and destroy it by flinging galaxies at it as projectiles.