List of top largest stock brokers in the world. Largest Brokerage Firms Below is the list of the largest brokerage firms in the United States and the world, known as "The big five brokerages" plus one of the most rapidly growing online brokers - Ally Invest. Best Brokerage Firms & Stock Trading Companies in 2019 Best Brokerage Firms in the USA. TD Ameritrade. Ally. USAA Brokerage. E*Trade Financial. Zacks Trade. Robinhood. Charles Schwab. Vanguard. Fidelity Investments. SogoTrade. Firstrade. Interactive Brokers. Lightspeed Trading. The 10 best brokerage firms above offer their customers online investing in the U.S. stock market (NYSE, NASDAQ, and S&P companies). Clients could either buy individual stocks or, to lower their risk exposure, they can purchase exchange traded funds as well as various mutual funds (index, target retirement, stocks, international and others).