Bulge bracket banks are the world's largest global investment banks, serving mostly large corporations, institutional investors and governments. The term "Bulge Bracket" comes from the way investment banks are listed on the "tombstone", or public notification of a financial transaction, where the largest advisors on investment banking operations are listed first. The term is primarily related to the financial advisory side of the business, as opposed to sales and trading.

Investment banking pertains to certain activities of a financial services company or a corporate division that engages in providing advisory-based services on financial transactions for clients, such as institutional investors, corporations, and governments. Traditionally associated with corporate finance, such a bank might assist in raising financial capital by underwriting or acting as the client's agent in the issuance of debt or equity securities. An investment bank may also assist companies involved in mergers and acquisitions (M&A) and provide ancillary services such as market making, trading of derivatives and equity securities, FICC services or research. Most investment banks maintain prime brokerage and asset management departments in conjunction with their investment research businesses. As an industry, it is broken up into the Bulge Bracket, Middle Market, and boutique market.