Big Three (management consultancies)

The Big Three or MBB refers to management consulting firms McKinsey & Company, Boston Consulting Group, and Bain & Company. The three companies are distinguished by the depth and rigor of their analyses and recommendations, rich histories of service dating back to their foundings in the mid-20th century, and strong client bases spanning some of the world's largest and more important companies.

The MBB firms recruit consultants from universities, MBA programs and industry. While historically associated with strategy consulting, they also provide services in areas such as operating model design, performance improvement, mergers and acquisitions due diligence, human capital and digital transformation.

MBB firms have also been the subject of criticism over the years for alleged unethical activities, with a prominent example being McKinsey's role in helping Purdue Pharma "turbo-charge" its sales of OxyContin, which has been cited as a direct contributor to the opioid epidemic in the United States.