Finale Season

Some series get cancelled and Cut Short. Other series last far longer than any fan had wanted and become a Franchise Zombie. But some series decide to end the show on their own terms, long before the network decides to cancel them and before the fans begin to tire of them.

This is not simply the last season of a series or a celebration of a series that ends before it can become a Franchise Zombie. The defining characteristic of The Final Season is that it is a planned final season and is announced as such from the very beginning. The Final Season will work to tie up any loose ends and answer any unanswered questions. During the Final Season, the writers may feel the freedom to tackle themes and stories they would otherwise not attempt, and to upset the Status Quo so much, they risk Jumping the Shark. Think of it as a Grand Finale, but stretched across an entire season.

As an Ending Trope, Spoilers ahead may be unmarked. Beware.

Examples of Finale Season include:

Live-Action TV

The final season of Lost distinguished itself from the other seasons by attempting to answer the big questions concerning the island, instead of posing more. A new plot device was introduced revealing the existence of a possible alternate Universe. The characters found themselves involved in a massive centuries-old power struggle.
The final season of Hannah Montana is so special, they changed the name to Hannah Montana Forever. This season brings us a change of residence for Miley, a change in the romantic pairings, as well as Miley revealing her secret to the entire world.
The tenth season of Friends was known to be the final season, so once the fallout of season 9 had been dealt with, the series immediately started building towards the Grand Finale & gave everyone closure. Except Joey, who not only didn't get an ending to his character arc, but also had absolutely no set-up for his spin-off series.
Smallville put the words "The Final Season" above the title in the commercials for its tenth season.
- In fact, the "previously on" sequence at the beginning of the season premiere ends with Tom Welling's (Clark's actor) voice saying "And now, the final season of Smallville".
Similarly, all the commercials for the episodes of the last season of Monk always had the tagline of it being the final season.
The last series of Ashes to Ashes was explicitly made out to be the last in pre-broadcast trailers, and functioned as both the final series of Ashes to Ashes and an epilogue to Life On Mars.
For the final season of Murphy Brown, show creator Diane English returned and gave the show an almost complete overhaul. The biggest change was a season arc in which Murphy is diagnosed with cancer, thus giving the show more gravitas. Also, Miles Silverberg was written out and replaced by a new executive producer played by Lily Tomlin, and Phil, who was killed off a few seasons back, was brought back, his death Ret Conned as going into hiding because of all the secrets he knew about Washington.
For the final season of Roseanne Roseanne won the lottery and had lots of OOC adventures; it turned out in the end to be all just a book she was writing to get over the fact that Dan had died of a heart attack.
Buffy the Vampire Slayer established pretty quickly that the seventh season's Big Bad was the First Evil, a being manifested from all evil in existence, and the season was then spent on Buffy getting an army together to fight the First Evil when it finally entered the physical realm.
The Wire saw cameos for nearly living character that had previously been Put on a Bus as well as the resolution of numerous story arcs and fairly definitive endings for numerous lead characters with things more or less coming full circle in the finale.
The last season of Star Trek: Deep Space Nine closed out the Dominion War arc with a bang, switching to a fully serialized format for the final ten episodes, showing massive space battles and finishing up every character's development and personal arcs.
Chuck's fifth season was announced and advertised as the final season.
It was pretty much known from the beginning that season eight would be the final season of Magnum, P.I...
Season eight has been announced as the final season of Desperate Housewives.
After One Tree Hill was renewed for a ninth season, it was confirmed as the final season.
The final season of ER resolved several storylines, and brought back many members of the show's beloved original cast.
The fifth season of Breaking Bad has been announced as the final season.
The fifth season of Fringe was announced as it's final season.

Western Animation

Teen Titans previously had Half Arc Seasons focusing on a specific member of the team. The final season focused on Beast Boy, but also used the season to introduce a large number of teenage superheroes and villains, establishing an international Teen Titan network. The very last episode, "Things Change", also (sort of) resolves Terra's arc.
Avatar: The Last Airbender was planned as a three season series from the get go, even having the seasons named Book 1, Book 2 and Book 3, like a book trilogy. Book 3 was their Finale Season, in which the battle with the Big Bad gets resolved and all loose ends are tied up.