X-Men: First Class
X-Men Origins: Wolverine
X-Men 1
X2: X-Men United
X-Men 3: The Last Stand
The Wolverine
X-Men: Days of Future Past — The Rogue Cut
X-Men: Apocalypse
X-Men: Dark Phoenix
Deadpool 1
Here’s the tricky part, Deadpool 2 is chronologically set next, however it does contain a major spoiler for the chronologically final film Logan. With that said if you haven’t yet seen either of these movies, I strongly suggest watching Logan first, then Deadpool 2 (I personally prefer the Super Duper Cut).
Deadpool 2 — The Super Duper Cut
Logan