There are many city-planets in Star Wars canon, ranging from the galactic capital of Coruscant to the Hutt homeworld of Nar Shaddaa. Inspired by Isaac Asimov's Foundation novels and short stories, George Lucas always intended the capital of the Star Wars galaxy to be a city-planet (also known as an ecumenopolis). Novelist Timothy Zahn honored this when he introduced the planet Coruscant in his "Thrawn trilogy," and Lucas incorporated this world into the prequels. Since then, though, there have been several other Star Wars city-planets.
Not all of them are canon, of course. Over the decades, the Star Wars Expanded Universe introduced many city-planets; these stories were branded non-canon (or "Legends") when Disney acquired Lucasfilm in 2012, though, so they shouldn't really be counted. Although some have been name-dropped in Star Wars ever-expanding canon since, some worlds seem to have been switched up significantly, so this list will only mention city-planets confirmed in canon.
8 Coruscant
The most well-known Star Wars city-planet is, of course, Coruscant. Generally believed to be the homeworld of the human race, Coruscant is situated in the Core, perfectly positioned around a number of stable hyperlanes that connect it to other worlds. The surface of Coruscant is entirely covered by one enormous city, and in fact only its highest peak - Umate - is uncovered (and can be seen at Monument Plaza). The lowest levels of Coruscant are entirely uninhabitable, and in fact few have ever visited them - with one notable exception being Princess Leia, who took a joyride into the lower levels while studying to become a senator. Coruscant was galactic capital through the prequels and original trilogy, but lost its status after the Galactic Civil War.
7 Hosnian Prime
The ill-fated Hosnian Prime has been described as another ecumenopolis (although some sources have suggested sub-districts retained their old city names). Located along a major hyperspace trade route, it is known to have hosted major factories and industrial complexes. Palpatine went to great lengths to ensure inhabitants of the Core Worlds were satisfied with his reign, but he seems to have been unsuccessful with Hosnian Prime, which is known to have been sympathetic to refugees. The planet eventually became capital of the New Republic after the end of the Galactic Civil War, but was tragically destroyed by Starkiller Base in Star Wars: The Force Awakens.
6 Denon
Many ecumenopolises are situated in the Core of the Star Wars galaxy map, and Denon is no exception. In the old Expanded Universe, this ancient city-planet was site of many battles between the Jedi and the Sith. It became an Imperial fortress world, and later became the temporary galactic capital after Coruscant was devastated by extragalactic invaders called the Yuuzhan Vong. In canon, Denon remained an Imperial stronghold, and seceded to the First Order at the first opportunity.
5 Eufornis Major
Little is known about the Star Wars city-planet Eufornis Major, which has only been name-dropped a handful of times. It was first mentioned in Jason Fry's novel Servants of the Empire: Rebel in the Ranks, and more recently referenced in Andor. Hopefully Star Wars will eventually reveal more about this Core World.
4 Troithe
It's possible Troithe was a Sith haven during the High Republic Era. A city-planet situated in the Mid Rim, Troithe had actually been a rival for Coruscant, but it was unable to remain competitive.
"As Coruscant's production had waxed, Troithe's waned due to factors both unavoidable (the exhaustion of precious mineral resources on the broken continent; the Cerberon system's decreasing accessibility in a Republic expanding into the Colonies and the Inner Rim; the gradual decay of Troithe's planetary orbit as it spiraled toward the black hole) and tragically preventable (a short-lived civil war between the mixed-species underclass and the majority human population - a conflict manipulated in part by an ambitious aristo-mercantile family seeking to profit)."
The Sith are known to have been active on Troithe, with a secret dark side stronghold in the asteroid belt around the Cerberon singularity. It is entirely possible they orchestrated the planet's economic downfall.
3 Empress Teta
An important world in Star Wars Legends, Empress Teta appeared in the classic Tales of the Jedi comics by Kevin J. Anderson and Tom Veitch. Situated in the Deep Core, it is named for a ruler who played a key role in the ancient Great Hyperspace War. In more recent times, it became dominated by the Mining Guild, and sided with the Separatists during the Clone Wars. Loyalist nobles fled to Coruscant, and were installed as puppets by the Empire after the end of the Clone Wars. Empress Teta was a strategically important world, with experimental Interdictor technology limited Rebel Alliance access to the Deep Core.
2 Nar Shaddaa
Sometimes called the Smuggler's Moon, Nar Shaddaa is the moon of the Hutt homeworld, Nal Hutta. Most Hutt crime lords operate from Nar Shaddaa, which was a particularly important planet in the Outer Rim - especially during the High Republic Era, before the Republic charted hyperlanes from the Core to the Rim. Described as an entire world of pirates and outlaws, Nal Hutta was generally considered the most dangerous place in the galaxy - which didn't stop Luke Skywalker heading there in search of Jedi secrets. The Rebel Alliance considered sending covert units to Nal Hutta to be a suicide mission.
1 Taris
Another ecumenopolis in the Outer Rim, Taris played a key role in the Knights of the Old Republic games and comics. It has striking similarities to Coruscant, with the wealthy living on the higher levels on one side of the planet - while the poor live in slums such as the Talinn District. Taris suffered an unknown tragedy at some point in the past, its surface littered with ships, many buildings destroyed, and the atmosphere becoming heavily polluted. Taris has turned up a few times in Star Wars canon, with Grand Moff Tarkin pursuing campaigns there.
Some other Star Wars planets have been called ecumenopolises, including the planet Wind in the Chinese web-comic Vow of Silver Dawn, but they do not appear to be true city-planets - with parts of their surface not covered. For now, then, city-planets remain surprisingly rare in Star Wars, however famous some of them may be. Hopefully the franchise will continue to explore them.