Now that Civilization V has had a few years to mature, it's gone from Civ IV's scrawnier younger sibling to a full-grown adult (it's even shaving now, we hear). Firaxis' official patches and expansions—Gods & Kings, and now the upcoming Brave New World—have done a lot to help fill-out Civ V's feature set, but the amazing modding community has also been twisting knobs and adding content, with over 1500 mods available on Steam Workshop.
This list features most of our favorites of the bunch, but we've opted to leave out single civs and single maps (of which there are many) to focus on interface, graphics, and larger gameplay and campaign mods. For a quick glance at all our recommendations, check our Steam Workshop collection, and you're encouraged to recommend your favorites in the comments.
Utilities and Interface Tweaks
Civ V Unofficial Patch
Start here. The Unofficial Patch is a collection of upgrades which add detail to the interface such as promotion icons over units, city banners which show turns until border expansion, and an improved city view. Those and many more tweaks make it easier to see data at a glance, and there are also tools for modders, if you're looking to make this list's next addition.
You'll need the Gods & Kings version of the Unofficial Patch if you want to enjoy the G&K Enhanced Mod mentioned later (and I recommend you do). If you don't own the Gods & Kings expansion, grab Vanilla Enhanced, which includes the original Unofficial Patch.
Really Advanced Setup
Since we're all Really Advanced Players here, we can use Really Advanced Setup to do really advanced things. Really Advanced Setup lets you deactivate civs we don't want randomly chosen, decide if you want to start near the ocean, a river, or in a certain biome (grass, plains, hills, forest, etc.), set starting bonuses, change starting units, and more.
As I already obsess over designing the perfect starting scenario, this mod is dangerous—try not to spend more time tweaking resource distribution than playing.
PerfectWorld3
Using Perlin noise, PerfectWorld 3 builds an elevation map to create landforms, then uses "a simplified model of geostrophic and monsoon wind patterns" to generate climate—the results as I've observed them are notably more natural maps. The version on Steam Workshop was not uploaded by the creator, but works, and the original thread can be found at Civilization Fanatics.
City Limits
With a city or Settler selected, City Limits displays the maximum area city borders can expand into. With a Settler selected, it also shows the overlap your potential new city will have with adjacent settlements, which is useful for optimizing placement. Make this simple but very helpful mod yours on Steam Workshop.
Faster Aircraft Animations
Don't start an industrial revolution without it! Get it on Steam Workshop.
InfoAddict
If you graphed the crossover between people who like Civ V and people who like graphs, you'd be wasting your time—everyone likes graphs. Get lots of them with InfoAddict, which comes in Gods & Kings and vanilla flavors and charts the world's progress, international relationships, and demographics with unmatched detail.
Graphics Mods
R.E.D. Modpack
R.E.D. started back with Civ IV, and stands for Regiment and Ethnic Diversity. It adds visual variation to the units and adjusts their proportions so that tanks are no longer accosted by giant infantrymen and aircraft carriers aren't eclipsed by Renaissance Era ships. R.E.D. also changes up the formations so the units look less like they were copied and pasted into their tiles.
Get it on Steam Workshop.
R.E.D. Xtreme
Install the original R.E.D. Modpack first, then R.E.D. Xtreme to shrink and multiply your units' individual actors even more. People smaller than hills? What crazy ideas will the modding community come up with next? Civs which don't all issue identical uniforms?
Ethnic Units
With some reference help from the R.E.D. Modpack, Ethnic Units also diversifies the look of each civ's infantry and vehicles with reskins. It may not be wholly complete (I'm afraid I haven't spawned one of every available unit from every civ for scrutiny), but it makes an easily identifiable difference and is being updated continuously—as of this article's posting, the last change was made yesterday.
Gameplay and Total Conversion Mods
G&K Enhanced Mod
Along with the Unofficial Patch (which is required to use it), the Gods & Kings Enhanced Mod touches every mechanic in Civ V. The AI is more rational, barbarians are much tougher, and just about everything has been rebalanced.
One of my favorite, smaller features is its Oregon Trail-like decision prompts, such as "frequent seasonal floods of this river provide unusually fertile topsoil for farming," with options to pay for new irrigation canals, research better ways to protect homes from floods, or let the locals handle it. Really, all you're doing is spending gold to earn a little extra Science, city-state loyalty, or what-have-you, but the prompts add flavor to the story of a city and civilization.
Get it on Steam Workshop—if you don't have Gods & Kings, grab the vanilla version instead. It should be noted that quite a few commenters have reported significant bugs—I haven't been able to replicate them yet, but if you need to troubleshoot, there's a forum for that.
R.E.D. WWII Edition
Unlike the R.E.D. Modpack on the previous page, which just adjusts the looks of units, R.E.D. WWII is a total conversion World War II scenario pack. More than just some maps that look a bit like Europe, it adds features such as capturing and liberating tiles, supply lines, reinforcements, and hotseat play.
This collection on Steam Workshop includes the two mods required, R.E.D. WWII Data Files and R.E.D. WWII Edition, as well as a couple recommended mods, including a version of R.E.D. Xtreme which works with the conversion to scale down the units. Note that most of your other mods will not likely be compatible with R.E.D. WWII.
Prehistoric Era
If ancient history just isn't ancient enough for you, try cultivating a great civilization starting 2000 years prior to the invention of writing. Prehistoric Era kicks things off with cavemen and rock paintings, adding 10 technologies, five buildings, and four new units. City growth and research are a bit more sluggish until you reach the Classical Era, so you're in for quite an epic if you plan to play from the Prehistoric Era all the way to Giant Death Robots.
Civilization Nights
Civilization Nights deserves recognition just for being as massive as it is—it may be the most comprehensive overhaul of Civ V there is. The total conversion makes significant rules changes (Happiness is most notably revamped) and advertises over 50 new buildings and wonders with custom artwork, dozens of new units with their own models, new policies, a restructured tech tree, and as many tweaks as there are stars in the night sky. Well, not that many, but a lot—the details can be found in its Civilization Fanatics thread.
Unfortunately, Nights hasn't been updated since October of last year, but if you can get past any bugs or unfinished bits you may encounter, it's a unique way to experience Civ V.
A Mod of Ice and Fire
If George R.R. Martin killed your favorite character in A Song of Ice and Fire or HBO's Game of Thrones series—and, spoiler, he probably does—you can design your own hexagonal fate for the fantasy series' warring families. A Mod of Ice and Fire is the best GoT mod I know of—all 10 new leaders have unique traits and special units and buildings, the religions, Great People, and spies have been renamed, and the technology tree appropriately ends in the Renaissance Era. It also comes with a Westeros and Essos map, a just-plain Westeros map, and a map of The Known World.
Grab A Mod of Ice and Fire on Steam Workshop (requires Gods & Kings).
Yet (not) Another Earth Maps Pack
You've got to have a good earth! There are tons to choose from, but I like Yet (not) Another Earth Maps Pack for the variety it offers in one package. There are several maps here—including Europe and Mediterranean maps as well as the whole of earth—and some added setup features.
With the mod loaded, select "custom game" to get to its custom start screen, where you can select a version of earth, and adjust city-state placement and resource distribution.
Strange and Historical Religions
The names and icons of religions are just for flavor, but its still a treat to found the Brotherhood of Nod, Church of Star Trek, Pastafarianism, or any of the other fictional and real religions and philosophies included in the Strange Religions pack. Objectivism vs. Scientology, fight! Actually, please don't.
If you prefer more historically significant faiths, the Historical Religions mod will give you fun, hard to spell religions such as Tlateomatiliztli, Pesedjet, and Forn Siðr, complete with custom icons and their own Civlopedia entries. If you need even more ideological fidelity, grab the Historical Religions Schisms Addon too and divide Christianity into Roman Catholicism, Eastern Orthodoxy, Oriental Orthodoxy, and Protestantism.
Steam News 