Bella Hadid's readying for legal battle with Adidas ... with sources telling us she's hired legal counsel to take on the athleticwear giant.
Sources with direct knowledge tell TMZ ... Bella's retained lawyers to take action against Adidas for their lack of public accountability -- basically, saying she feels they spearheaded a cruel and damaging campaign.
Our sources say she's upset the company would put out a campaign that would associate anyone with a tragedy like the Munich Massacre at the 1972 Olympics .