Do I need to complete AC3 to understand AC4?

Solution 1:

No - as far as I can tell, the stories are almost entirely unrelated.

Solution 2:

There are absolutely no references to AC3 in the main (Edward Kenway) section of the game. In the Abstergo Research Assistant position, there are one or two videos about the ending of AC3, but it is not related to the story.

Some characters from the present-day section of past AC games make a small appearance in ACIV, but they directly don't play a major role in the story, and the parts they do play have nothing to do with any previous game.

You will be able to fully understand the game's plot without playing AC3

Solution 3:

There is a relation between AC4 and AC3 where in AC4, you will play as Edward Kenway who is the father of Haytham Kenway and grandfather of Connor Kenway in AC3.