Who rules small towns of cities?

[Caged Maiden]

Nobles, whether Dukes, Earls, Whatever, owned LAND, whether it had a town or a couple tiny backwater villages on it. If you were making say, a medieval (1200's) Paris, you could do some research on how it was structured politically and socially (I don't happen to know much on that). All the above comments point out some really good things. Some medieval towns were completely founded by merchants. Guilds held loads of power, driving out who they didn't want in the city. Mayors were completely commonplace, as were other appointed officials. You have law-men, sheriffs, provosts; whatever they were called depending on their region and time period, religious leaders (don't underestimate the power over every-day life that they held). There were also kings, of course who oversaw the whole of the land, but how could they function without their ministers, lords, minor nobles, etc. down the ranks. It is also likely that the various factions mentioned would not see eye-to-eye (they never did).
Just a suggestion... if you are modeling your world after a certain earth time period, you might want to read a little about the political and social structure of that period.
When I write a village, a town or a kingdom, I ask myself, "Why does a city council work here? How does this mayor compete with these Guilds/Warlords/ Nobles? Would the king/Mayor?Lord get involved with this, or would the constables/city guard/night watch take care of it themselves?"


KEEP READING IF YOU'D LIKE A LITTLE HISTORICAL VIEWPOINT
A lot changed in Europe between 1300 and 1600 and the social structure of the whole continent changed after the plague, when the population no longer was divided into the very wealthy and the very poor.
The plague killed landowners as easily as it killed beggars, and the result was loads of land left vacant, which was bought up by rising merchant-class families. The Renaissance (1500's) in England was COMPLETELY different than the medieval period. I usually use the 1500's as my inspiration because more people (all but the very poorest) had more freedoms, rights, and opportunities than in earlier periods when social class was a bit oppressing. Also, the idea of more people splitting the power appeals to me because I like conflict. Okay so here's an example of power structure in Elizabethan England: A lord dressed his household staff in livery. When a servant took his lord's cloth, he owed loyalty and services to his lord, but also shared in is lord's exemption from certain laws. Peers could not be arrested except for treason, felony, or breach of peace, and neither could anyone in their livery. Not a bad deal for a common man.
OKAY that doesn't have much to do with who rules a town, but my point was that MANY people could rule the town regardless of the one guy at the top.

[Map the Dragon]

Ok...these are from the top of my head in totally random order. Also note, that many of these have feminine equivalents.

governor
duke
king
prince
lord
chieftan
baron
magistrate
viscount
arch-duke
count
marquis
council
collective
minsister
chancellor
premier
pharoah
imam
judge
khan
sultan
maharaja
viceroy
fuhrer
head
sir
regent
bailiff
protector
protectorate


In my novel, I tended to use some of the known entities, and made up others. I think that we doing so, the mix should be measured. Too many made up titles and such gets confusing. For instance, in one culture that mimicks medieval society, I choose some of the above, while in entirely original social constructs I made up titles and the like altogether. The latter tend to be my favorite and for readers have the most flavor, if it's not overbearing.

[Hans]

If that city is ruled in the name of a higher noble a reeve (or vogt) might be there to rule. Seldom the nobles do this directly in a city.

[Ravana]

Very often, cities were areas where the nobility did not rule. That was one of the major factors that contributed to their growth: "Stadtluft macht frei" ("City air is free air"), as it was put in the Holy Roman Empire—which had between fifty and eighty-odd Free Imperial Cities, depending on the time period you're looking at, all of them answering directly to the emperor. This was also why cities such as Paris and London played disproportionate roles in the development of their nations: the cities were political entities which were entirely outside of the normal channels of authority. So unless you actually want a noble to be in charge, go with some form of civilian administration. As anihow noted, nobles owned land—and there wasn't much of that to be found within a city's walls. The main exception I can think of (as far as the more familiar periods of European history go) was the city-states of Italy during the Renaissance and later periods, where the reigning noble of the state usually was also the one in charge of the city… usually, though not always.

Of course, the people who tended to make up the civilian administration also tended not to be from the lowest classes… but then, a middle class was one of the things that was both created by and spurred the growth of cities. Who these people are will depend on your setting. Mayors, burghers, aldermen, councilors, guild or merchant organizations, possibly the occasional clergyman. How they were chosen will also vary widely: anything from appointment by the monarch to inherited office to election (usually by a small number of "qualified" voters: universal franchise didn't come along until fairly recently).

Look up "free city" and also "chartered city" for good examples.

[Antaus]

Who ruled cities or towns could vary depending on the setting, kingdom, culture, and many other factors. If you're going with stock fantasy, then it could vary. Nobles with high titles like Duke usually ruled entire regions in the name of their king (a duchy), and the pyramid goes down from there. Depending on the size of the town/city, the ruler could be a governor (they had a LOT more power in those times), even a sheriff, like the Sheriff of Nottingham. Also, the ruler of a small city of town could even be a low ranking noble, Baron for instance. Also, for reference purposes:

Landed gentry is a traditional British social class, consisting of land owners who could live entirely off rental income. Often they only worked in an administrative capacity looking after the management of their own lands.
The term "gentry" included four separate groups in England:

Baronet. This was a position created by King James in 1611 giving the person the hereditary right to be addressed as "Sir."

Knight. This was originally a military honor, but was increasingly used in a secular manner as a reward for service to the Crown.

Esquire. This was originally a title related to the battlefield. It included a squire or person aspiring to knighthood, an attendant on a knight, and was later an honor that could be conferred by the Crown. It later included certain offices such as Justice of the Peace.

Gentlemen. This started as a separate title with the statute of Additions of 1413. It was later used generally for a man of high birth or rank, good social standing, and of wealth who did not need to work for a living.

~ Wikipedia

A good idea would also be to research nobility, monarchy, feudalism, including specific noble titles that you would want to use in a story.