The movie "The Wolverine" (2013) covers, of course, Wolverine. Is it in canon with the previous X-Men movies?
More specifically, which movies should one have already seen in order to understand this film?
Because this takes place after the events of X-Men 3: The Last Stand and makes references to those events, it can be assumed that it is within the original three X-Men movies in terms of canon.
To understand the turmoil Wolverine is experiencing in the movie, you might want to see X-Men, X2, and X-Men: The Last Stand.
The movie that will tie X-Men: First class with the three original X-Men, and The Wolverine is X-Men: Days of Future Past. This movie has the original X-Men cast as well as the younger cast from First Class.
While the film is in canon with the others, it is not necessary to have seen the other movies to understand almost all aspects of the movie, becuse they only share a couple of characters. I saw it with someone who had no experience with the X-men franchise and the only thing that they found unclear was the post-credits stinger because it involves characters from X-men, and whether
he killed Jean Grey or just injured her prior to the events of the movie which is eventually clarified anyway.