Quick answer
Does Boa Hancock have Conqueror's Haki?
Verified through chapter 519Updated
What the manga shows
4 factsHancock states that Luffy has the same Haou-type Haki as her.
Marigold confirms her sister is the only person she has seen use that power before Luffy.
Boa Hancock realizes Luffy has the same Haou-type Haki as her.
Warriors identify the power Luffy used as Haou-type Haki, the Haki of the chosen ones.
Change log
1 chapter- Chapter 519Added 4 facts; updated the answer