[Intro]
G    D     Am    G    D     C
                   Oo oo-oo oo
G    D     Am    G    D     C
  Oo oo-oo oo      Oo oo-oo oo

[Verse 1]
G                D                Am
  Mama take this badge off of me
G         D               C
  I can't use it anymore
G              D                      Am
  It's getting dark, too dark to see
G            D                     C
  I feel I'm knockin on heaven's door

[Chorus]
G               D                    Am
  Knock, knock, knockin' on heaven's door
G               D                    C
  Knock, knock, knockin' on heaven's door
G               D                    Am
  Knock, knock, knockin' on heaven's door
G               D                    C
  Knock, knock, knockin' on heaven's door

[Verse 2]
G             D                   Am
  Mama put my guns in the ground
G         D               C
  I can't shoot them anymore
G                 D               Am
  That long black cloud is comin' down
G            D                      C
  I feel I'm knockin' on heaven's door

[Chorus]
G               D                    Am
  Knock, knock, knockin' on heaven's door
G               D                    C
  Knock, knock, knockin' on heaven's door
G               D                    Am
  Knock, knock, knockin' on heaven's door
G               D                    C
  Knock, knock, knockin' on heaven's door

[Outro]
G    D     Am    G
  Oo oo-oo oo   (fade)

Source: Ultimate Guitar