How many open season movies are there?

There is only one "Open Season" movie. It was released in 2006.

However, there are three "Open Season" direct-to-video sequels:

* Open Season 2 (2008)

* Open Season 3: American Tail (2010)

* Open Season: Scared Silly (2013)

So depending on how you define "Open Season movie", there is either one or four movies in the franchise.