The Marvel cinematic universe has been releasing films for over 10 years now and with so many cross overs and films interlinking with each other, it can be hard to establish the chronological order of the universe.
Fortunately, I've done some research into the timeline and figured out the Marvel cinematic universe.
1) Captain America - The First Avenger
2) Iron Man
3) Iron Man 2
4) The Incredible Hulk
6) Avengers Assemble
7) Iron Man 3
8) Thor - Dark World
9) Captain America - Winter Solider
10) Guardians of the Galaxy
11) Guardians of the Galaxy - Vol 2
12) Avengers Age of Ultron
13) Ant Man
14) Captain America - Civil War
15) Doctor Strange
16) Spiderman Homecoming
17) Thor - Ragnarok
18) Black Panther
19) Avengers Infinity War
If you want to watch all of the above, it should take you around 9 days. So get comfortable.