how many films are there in that series?
Three
The Hobbit (film series)
The Hobbit is a film series consisting of three high fantasy adventure films directed by Peter Jackson. 
who plays gandalf in the hobbit an unexpected journey Ian McKellen
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The Hobbit (film series) [SEP] Introduction
The Hobbit is a film series consisting of three high fantasy adventure films directed by Peter Jackson. They are based on the 1937 novel "The Hobbit" by J. R. R. Tolkien, with large portions of the trilogy inspired by the appendices to "The Return of the King", which expand on the story told in "The Hobbit", as well as new material and characters written especially for the films. Together they act as a prequel to Jackson's "The Lord of the Rings" film trilogy. The films are subtitled "" (2012), "" (2013), and "" (2014). The screenplay was written by Fran Walsh, Philippa Boyens, Jackson, and Guillermo del Toro, who was originally chosen to direct before his departure from the project.