Rancher

Simply put, the owner of a ranch, a spread of land where animals are raised. In The Western, usually this is cattle, but sheep, chicken and (in the modern day) ostriches are all potential ranches.

The Rancher employs the Cowboy, Camp Cook and other ranch workers. He (or sometimes she) is the equivalent of a business owner in a more urban setting. They generally will dress a little better than their employees, but not too much—most ranchers are hands-on to some degree, and need to be able to do anything an ordinary cowboy could. Indeed, many a cowboy has the ambition of gaining a ranch of his very own.

In fiction, the larger the ranch is, the more likely the rancher is to be the bad guy of the story. This is not a hard and fast rule (the Cartwrights of Bonanza have an immense spread, but are salt of the earth types), but that's the way to bet. If the rancher owns several ranches, or one big enough to count as its own feudal country, they become a Cattle Baron.

"Saving the ranch" is a common plotline for Westerns, especially in B-movies, as a couple of bad years could put a small rancher on the verge of bankruptcy.

Examples of Rancher include:

Film

The ranch owner who needs the Cattle Drive done in City Slickers
Night Of The Wolf: A Determined Widow heroine rancher.
The Journey of Natty Gann (minor characters)
Joe Bannock in A Town Like Alice. Though he didn't own it til the end, if memory serves.
The Cowboys: Wil Andersen has to hire young boys when his cattle drivers head for the gold fields.
Big Jake: The McCandles ranch is run over by a gang of cutthroats.
Chisum: Very loosly based on the Lincoln Country War.
McLintock!: George Washington McLintock
The Man Who Shot Liberty Valance: Tom Doniphon had a small ranch.
Dan Evans in Three Ten to Yuma, who takes a job escorting a criminal so he can help support his ranch.
Beans in Rango owns a ranch that the mayor of town wants to purchase from.
Bick Benedict in Giant.

Literature

'Ole Devil' Hardin in the Western novels of J. T. Edson.
- Also John Slaughter.
The Sci Fi novel Malevil has an interesting example. Before World War III, the main character is a rural French rancher who expands his property to include an old castle. He keeps the usual livestock and grazing land but also stables some his animals in a cave under the keep. He also runs a vineyard, produces wine, and had plans to reopen the castle to tourists.
Luke Fletcher in Shane is an example of the Big Bad Rancher.

Live Action TV

The Cartwright family of Bonanza, as mentioned above, provided that Ben doesn't slip into outright Cattle Baron territory.
In one Magnum, P.I. episode there is a teenage rancher who needs our heroes' help.
The Kents' farm in Smallville is an important element.
In order, Judge Garth, the Grainger brothers, and Col. MacKenzie, owners of the Shiloh Ranch in The Virginian (later The Men From Shiloh).
On Firefly Malcolm Reynold's mom ran a ranch.

Tabletop Games

Traveller : The ideal Aslan noble family owns a ranch. As Aslan are a Proud Warrior Race the male is supposed to hold it by virtue of his status as a Real Man.